Silicone Glove Mold and Fiberglass Mothermold

November 14, 2017

With larger pieces, it is more cost effective to make a glove mold rather than a large block mold. A glove mold is also less cumbersome than a large block mold. Glove molds do need a supportive structure since they are thinner than a block mold, so I will make an epoxy and fiberglass mothermold to support the finished glove mold. Additionally, the piece I picked for this project has a lot of detail so I will be using a silicone diluent to pick up all the detail and decrease the risk of air bubbles.

Materials needed:

  • Original part
  • AeroMarine Products 128 Silicone with Brushable Catalyst
  • AeroMarine Products Silicone Diluent
  • AeroMarine Products 300/21 Epoxy Resin
  • AeroMarine Products 6oz Plain Weave Fiberglass Cloth
  • Scale
  • Measuring and mixing containers and utensils
  • Piece of cardboard large enough for original to sit on
  • Inexpensive brushes (I used 1 inch chip brushes)
  • Gloves
  • Scissors for trimming fiberglass

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • To start, I set my original on the cardboard, right in the middle. The mold needs to have a lip at the base. The cardboard is something that the silicone can be applied to and will peel off easily when I’m done.


  • Because of the detail on the original, I am using silicone diluent to thin the rather viscous brushable silicone. The diluent is added to the white silicone base (Part A) up to 10% by weight. For the first coat, I weighed out 150 grams of silicone Part A and added 15 grams of the silicone diluent and mixed well. The total weight of my silicone is now 165 grams and the catalyst needs to be added at 10% of the total weight. I rounded 16.5 grams up to 17 grams because my scale doesn’t do half grams. This silicone isn’t finicky or exacting, so you can round up or down. It will turn out fine either way.
  • As I applied the silicone using a 1 inch chip brush, I really focused on getting into all the nooks and crannies of the piece. This silicone has a 45 minute pot life which allows me to take my time and makes sure there are no air bubbles in my first coat of silicone. Any air bubbles in the first coat will be recreated as lumps in every casting. So while I try to avoid air bubbles in every subsequent coat, it is extremely important to not have any in the first coat.

  • I let the silicone cure for 24 hours. For the next two coats, I mixed 150 grams of Silicone Part A, 8 grams of silicone diluent (5%), and 16 grams of catalyst. The 2nd and 3rd coats can go on a little thicker to help build the mold. I also focused on making a “lip” all the way around the piece, extended about an inch out. I always let each coat cure for 24 hours before applying the next coat.


  • For the 4th and final coat, I went back to adding the silicone diluent at 10% because I want this coat to flow more into the remaining detail and be mostly smooth on top. This makes it easier to do the epoxy and fiberglass mothermold. I let the silicone cure for 24 hours before moving on to the next step.

  • Now that I have a nice smooth glove mold, it’s time to make an epoxy and fiberglass mothermold to support it. First, I peel the whole thing off the cardboard, taking care not to peel the silicone off the piece. I set it back down on the plastic covering on my work station. The epoxy peels easily off the plastic, but would stick to the cardboard.


  • I’m using our 6 oz plain weave fiberglass. Since this piece is mostly flat and not too large, I’m only going to do one layer of resin and fiberglass mothermold. If the piece was larger or more vertical, I would do several layers to give it more support.
  • I trimmed the fiberglass to fit comfortably around the mold and then set it in place. I pressed the fiberglass into the contours of the mold. This was fairly simple because I filled in most of the detail with the last coat of silicone.


  • Next I mixed 4 oz of AeroMarine Products 300 Epoxy Resin with 2 oz of AeroMarine Products 21 Epoxy Hardener. I stirred it vigorously, taking care to scrape the sides and bottom of the mixing container, for several minutes. Then, I dribbled the epoxy around the edges of the fiberglass to hold the edges down. I used my chip brush to apply more epoxy to fiberglass, saturating it completely.

  • If I needed to do more layers, I would let this set up for at least 12 hours and then follow the same procedure, this time laying the fiberglass in the opposite direction for added strength. Since I’m only doing the one layer, I just let it cure for the full 24 hours before coming back to remove the fiberglass mothermold and de-mold the piece.
  • The raw edges of fiberglass and epoxy were very sharp, so I used heavy duty scissors to trim and shape teh fiberglass mothermold.


  • Once the sharp edges were trimmed away, I carefully pulled the mold (with the piece still inside) away from the fiberglass mothermold. Then, I carefully removed the silicone mold from the piece.

  • If I was going to cast, I would then sit the mold back into the mothermold for the casting.

Done! This was just a simple glove mold with epoxy and fiberglass mothermold. The same method can be applied to larger and/or more complex projects. As every project is different, give us a call, toll-free, at 877-342-8860 or drop us an email at if you have questions about your own project!

Latex Storage and Winter Weather

October 30, 2017

Latex is a great mold making material that makes durable, long lasting molds for concrete, plaster, hydrocal and other non-exothermic casting materials. Finished latex molds have a long library life when properly stored as well. Howeve,r winter is coming and that can mean issues with shipping and storing uncured latex.

Our AeroMarine Products Mold Making Latex is a creamy white color with a smooth texture when uncured. It cures to a light beige color. Here is what our uncured, properly stored latex looks like:

To keep your latex viable, it needs to be stored indoors at a temperature between 60F and 72F. If the latex gets below 60F, it can freeze which ruins it. Frozen latex becomes clumpy and cottage cheese like and unusable. Once the latex has frozen, it cannot be revived and used again. Here is what latex that has been frozen looks like:

  Before and after stirring 

Do not store your latex in a garage, basement, shed or any other unheated building during winter. Proper latex storage should be indoors in a heated building in a locked cabinet or closet, away from any pets or small children. When kept at the appropriate temperature, your latex should last for six months.

On the shipping side of things, we put big “PROTECT FROM FREEZING” stickers on all the latex we ship out during the months of October-April. When shipping the latex to the East Coast and other colder climates, we also generally ship 3 day shipping instead of ground during the colder months. This reduces the time the latex may spend in cold weather in transit. We ask UPS to require a signature on latex shipped during the winter to ensure that no packages containing latex are left on porches during cold weather. This method works well. We generally don’t have an issues with our customers receiving frozen latex. However, if you receive frozen latex, you can email us a picture of the latex ASAP and we will send you a replacement.

Remember, proper latex storage is indoors, between 60F and 72F.  Latex should be used within 6 months from date of delivery. Remember to check the Technical Data Sheets for any other materials that you may be storing over the winter. Many have special temperature and storage requirements. You can also read these blog posts for more information:

Curing Issues- Trouble Shooting

If you have any other questions, drop us an email at or give us a call Monday-Friday 9am-4pm Pacific time at 877-342-8860.

Penny Tabletop with Epoxy

September 7, 2017

For this project, we are taking an old side table and refinishing it with pennies and epoxy. Penny epoxy counter tops, table tops, and floors are a popular project that we get asked about frequently. This post will walk you through doing a penny epoxy table top over wood. If you have any questions about doing a floor or counter top over concrete, you can always send us an email at or give us a call toll-free at 877-342-8860.

Materials needed:

  • Wooden table
  • AeroMarine Products 300/21 Epoxy Resin and Hardener
  • Water based wood stain
  • Acetone
  • Sand paper (I used 60 grit)
  • Lots of pennies (I used about $4.25 for a foot square tabletop)
  • Paper barrier mask and gloves
  • Plastic drop cloth or similar
  • Inexpensive brushes (I used 1 inch chip brushes)
  • Mixing and measuring containers and utensils
  • Blue painter’s tape
  • Paint (for the legs of the table)

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • First, I needed to sand the old paint off the top of the table. Our epoxy sticks to most paint but I want a lighter background for the pennies. I also want the epoxy to penetrate and bond to the wood, not the paint, so that there is no worry about de-lamination over time. I used 60 grit sandpaper to sand off all the old paint.


  • When I was done sanding, I wiped the table off with a dry rag to clean off all the wood dust. Then, I applied the first coat of my water based wood stain. It is a lot of work to get epoxy to stick to oil based stain, whereas epoxy goes over the water based stain easily. Follow the application directions for the water based stain that you choose. The stain I was working with said to brush on a coat and then wipe off any excess immediately and wait two hours between coats. I did three coats following those directions and then let stain set over the weekend.

  • While I was waiting for the stain to dry, I laid out my pennies. I chose to arrange them from brightest to darkest for a gradient look. This also allowed me to check the pennies and make sure none of them had large amounts of dirt on them.

  • On Monday morning, I brushed on a thin coat of AeroMarine Products 300/21 Epoxy using a 1 inch chip brush. The 300/21 is mixed 2:1, 300 resin to 21 hardener. I mixed up 3 ounces for the brush coat, which was a bit more than I needed but it kept the mix ratio easy to measure. Mixing up less than 3 ounces can make getting the mix ratio right rather tricky. Very small batches will also take longer than the standard 24 hour cure time. On Tuesday morning, I did the same process. The reason that we do a couple of brush coats first is to seal the wood and cut down on air bubbles when we get to the pour coats. On Wednesday morning, I brushed a coat of epoxy on and then set my pennies on the epoxy immediately after brushing on the epoxy. I like using the epoxy to glue down the pennies rather than using a super glue or something similar because it is one less product to purchase. Also, there is less space for air to get trapped under the pennies and cause air bubbles later.
  • Thursday morning, I checked to make sure the epoxy had set up and the pennies were glued into place. Everything looked good, so I taped up the edges of the table with painter’s tape to prep for the first pour coat.

  • It takes a couple layers of tape to make sure the bottom is sealed completely and the edge of the tape rises above the pennies.
  • I mixed up 6 ounces of epoxy for the first pour coat. I poured the epoxy on the pennies and then used a brush to spread the epoxy out. The aim of this first pour coat was just to fill in the spaces between the pennies. I like to do multiple pour coats because the thinner the pour, the easier it is for air bubbles to rise up to the surface and pop. Additionally, if there are any air bubble once the epoxy cures, it is easy to sand them out before doing the next pour coat.
  • After 24 hours, I pulled the tape off and checked for bubbles. There were a few bubbles on the surface and along the edge where the tape was. I sanded these bubble out with 60 grit sandpaper and wiped the whole table top with acetone on a clean rag. Then I taped the edges up again. Then, I mixed another 6 ounces of epoxy and poured another coat, this time covering up the pennies completely.

 Surface bubbles

Surface bubbles sanded out

  • I decided to do one more pour coat to give the epoxy more thickness and depth. After the third pour coat, I pulled the tape off and sanded down the edges where the epoxy met  the tape. The epoxy wicks up where it meets the tape so it is important to sand it flat. That also happens to be where bubbles like to collect, so sanding serves two purposes.

 You can see some bubbles and the wicking effect along the edge

  • The next step is to do a thin pour coat that flows over the sides of the table. Once the tabletop was all sanded, I spread out a large trash bag underneath the table. This table also has some slats that connect the legs near the bottom that I covered with tape to protect them from epoxy dripping off the edges of the table. I mixed up another 6 ounces of epoxy and poured it on the table and used a chip brush to spread it out a bit. The epoxy will run over the sides, so use the brush to brush the epoxy along the edge. Once the epoxy starts to gel, about 20-30 minutes, I used the back of a plastic knife to scrape the drips off.

 Drips hanging off the underside of the table

 Plastic knife used to scrape those drips off

  • If there are any bubbles once the epoxy has cured, you can sand them out and do a thin brush coat. Fortunately, I didn’t get any bubbles in the final pour! Now, I’m ready to paint the table legs.

                           Penny Epoxy Tabletop

  • Finally, I taped up the edges of the table and applied two coats of forest green spray paint. Follow the directions for the paint you choose in regards to surface prep and dry time.

 Taped edges, ready to paint

 All done, just drying


I got little green paint on the epoxy of one corner when I turned the table to paint the other side of the legs. It easily wiped away with some acetone.

This project was done on a small wooden table, but penny epoxy flooring, counter tops and larger tables are also common. Hopefully, this post gives you a good idea of the process. If you have any questions about the products used or general application questions, check out our website, or send us an email at or give us a call at 877-342-8860.


Silicone Mold to Modify a Fragile or Broken Original Part (Post 2 of 2)

July 12, 2017

This is a continuation of our last post about using silicone molds to modify a broken or fragile original part. In this post, we will go over sculpting in clay on the new piece and making a new mold. You can read the first part of this blog post here:

Materials needed:

  • AeroMarine Products AM128 Pourable Silicone
  • AeroMarine Products White Urethane Casting Resin
  • Urethane colorant
  • Mold release
  • Original part
  • Modeling clay
  • Mold box
  • Chip brush
  • Scale
  • Mixing containers and utensils
  • Gloves

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • Now that I have a original, I can use clay to sculpt directly on to it. I’m using non drying, sulfur free modeling clay. Because I’m using a non drying modeling clay, I want to make sure that what I’m sculpting will be able to be pulled from a one piece or clam shell mold. If I want to sculpt something more intricate, it would require a two part or multi piece mold. For a two part mold or multi piece mold, I would use a clay that air dries for sculpting and then use the modeling clay when making the mold. You can watch our video about making two part molds here:
  • I decided I wanted my part to have two versions, unicorn horn and monster horns. I cast two parts in urethane casting resin from the silicone mold and sculpted the unicorn horn on one and the monster horns on the other. If you want to save on materials, you can certainly use one cast, make the mold, remove the clay and then sculpt on that part again.


  • I reused the same plastic containers for these new molds, so I mixed up the same amount of silicone (900 grams part A, 90 grams of part B catalyst) as I used for the first mold. Because of the detail of these pieces, I again used a chip brush to brush a thin coat of silicone on to the pieces before slowly pouring the rest of the silicone into a corner of the mold box.


  • About 16- 24 hours later when the silicone cured, I removed the original part.
  • I checked to make sure the humidity was under 50%, sprayed a little mold release into the molds and got ready to mix up my urethane casting resin.
  • The AeroMarine Products White Casting Resin is mixed 1:1 by volume. Urethane colorant is always added to the part B and well mixed before combining the two parts. Make sure to mix vigorously for about a minute with a plastic utensil and then pour slowly into the lowest part of the mold. AeroMarine Products Urethane Casting Resin is ready to demold in 30 minutes. Because of the shape of the part with the horns, I found it is best to demold right at the 30 minute mark when the casting resin is still warm and a bit pliable. It makes it much easier to remove the part from the mold. Once the part is removed from the mold, I set it aside to allow it to continue hardening and cooling off.

  • The cast on the right was colored with green urethane colorant. The cast on the left was painted with orange glow-in-the-dark paint with the horns colored with permanent felt tip marker.

The final results! All of these were achieved by a combination of colored resin, paint, and felt tip markers. As always if you have any questions, send us an email at

Silicone Mold to Modify a Fragile or Broken Original Part (Post 1 of 2)

June 8, 2017

Sometimes, I have an original part that is either broken or that I want to modify in different ways. In this 2 part blog post, I am going to make several slightly different variations of this part. However, the original is a bit fragile. I don’t want to damage it by sculpting clay on it and then making a mold from it several times over. So, I’m going to make one mold, cast a piece in urethane resin, and use the urethane resin part to sculpt on and make new molds from it. If the part was broken, I would mold and cast the original and then use clay to fill in the broken areas of the original part.

Materials needed:

  • AeroMarine Products AM128 Pourable Silicone
  • AeroMarine Products White Urethane Casting Resin
  • Urethane colorant
  • Mold release
  • Original part
  • Modeling clay
  • Mold box
  • Chip brush
  • Scale
  • Mixing containers and utensils
  • Gloves

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • If your original is unpainted clay, old concrete or plaster, or another similarly porous material, seal it before making the mold. You can do this by painting the part, or using a sealant type material. For my clay original part, I used an clear aerosol urethane sealant.

  • Anchor the original to the bottom of the mold  box with a small amount of modeling clay. For this mold box, I used a plastic food storage box because it happened to be just about the perfect size. You can always make a custom mold box using cardboard and a hot glue as well. This blog post covers how to make a mold box,


  • I weighed out about 900 grams of the silicone Part A base and 90 grams of the Part B catalyst and mixed well until it was a nice uniform pale purple color. The mixing took about five minutes.
  • Since this piece has a lot of fine detail, I used an inexpensive chip brush to brush the silicone into the detail of the piece before pouring the rest of the silicone. This AeroMarine Products AM128 Pourable Silicone has a pot life of 45 minutes, so there was plenty of time to brush some on before slowly pouring the rest into the mold box.

  • 20 hours later, I removed the mold from the mold box and the original part from the mold. It took a little wiggling, because of the undercut of the beard, but it all came out in one piece.

  • Then, I ran into a problem. I will cast the piece in a white urethane. The weather here in San Diego was very uncooperative for about a week. It was overcast and muggy (June Gloom, we call it). The humidity didn’t get below 50%, which is the threshold for working with urethane. Urethane is very moisture sensitive before it is cured.  Mixing and pouring a urethane on a humid or rainy day will result a lot of bubbles in the piece. So, I put this project on hold until the weather cleared up.
  • When the weather finally cleared, I washed the mold with warm water and dish soap, patted it dry and then let it air dry as well. I did this because it had been sitting a dusty warehouse for over a week. Once it was completely dry, I sprayed some Urethane Mold Release into the mold and let it sit for a few minutes. This lets the propellants evaporate and leave behind just the mold release.

  • I mixed my AeroMarine Products Urethane Casting Resin 1:1 by volume, stirring vigorously for about a minute and then poured slowly into the mold. Not super slow because the pot life for the Urethane Casting Resin is only about 3-5 minutes, but slowly enough to let it flow through mold without causing air bubbles.


  • It’s hard to tell from the second picture, but all the little bubbles from pouring the material have popped and the AeroMarine Products Urethane Casting Resin is smooth and bubble free.
  • After thirty minutes, I popped the cast out of the mold. Because of the mold release, it came out very easily.

  • An excellent, sturdy replica of my fragile, original part.

In the next blog post, I’ll go over sculpting, re-molding, and using the urethane casting resin and colorant to create new pieces.

Roto Casting Resin in a Two Part Silicone Mold

May 12, 2017

Rotational or roto casting means rotating your mold continually while the resin sets up so that youget a hollow casting. Two of the most common reasons to cast this way are to keep the weight of the piece down and to save money on casting materials. For this post, I’m doing the roto casting by hand. The internet is full of plans and how-to videos for making rotational casting frames, either motorized or hand turned method. If you think roto casting is something you will be doing for a lot of your pieces, it’s definitely worth a Google search to see what’s out there.

Materials needed:

  • Two part silicone mold (refer back to this post if you haven’t made a silicone mold yet )
  • AeroMarine Products Urethane Casting Resin
  • Non-sulfur modeling clay
  • Tape (I prefer blue painter’s tape, but masking tape and other varieties are fine too)
  • Plastic mixing containers and utensils
  • Gloves
  • Urethane colorant (optional)

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • To start, I took my two part mold and taped it shut, leaving the vent and sprue (opening for pouring the product into) unobstructed.


  • I blocked the vent with some clay and then applied more tape to hold the clay in place.

  • Next, I got ready to mix the Urethane Casting Resin. This product is mixed 1:1 by volume. This mold usually takes about 14 ounces to fill, so I figured out that I would use about 6 ounces to do the roto casting. I measured out 3 ounces of Part A and 3 ounces of Part B. I mixed some blue urethane colorant into the Part B and then mixed both parts together. I carefully poured the resin into the sprue, wiped away the little bit that got on the outside of the mold, plugged the sprue with clay and taped it shut.

 Blue colorant mixed into Part B 

  • I marked the bottom of the mold with a star so I know which side to set the mold down on when I’m done rotating the mold. I want to set the mold bottom down so that any excess resin settles at the bottom of the casting. Otherwise, the casting will be heavier on whatever side the excess resin settles, making it prone to falling over.
  • Once everything was taped up, I picked up the mold and rotated it by hand for 10-15 minutes. I turn it every which way, so that the resin will completely coat the inside of the mold.
  • After 10-15 minutesof rotating, I set the mold star side (bottom side) down and let it sit for the remaining 15 minutes of it’s cure time.
  • After 15 minutes, I cut the tape off, opened the mold and popped out my casting. I trimmed a small amount of flash from the parting line and sprue.


This roto casting turned out nicely. As always, if you have any questions, about this or other projects, please send us an email at

Silicone Additives- Accelerator, Thinner, Thickener

May 1, 2017

Our tin catalyzed silicone, AeroMarine AM 128 Silicone Rubber, can be used with silicone additives that either decrease or increase the viscosity or speed up the cure time. Each of these silicone additives is added at different times in the mixing process and in different quantities to affect the silicone. These additives are the proper way to control viscosity and speed up cure time. Please do not mix silicone with both the pourable (purple) and brushable (pink) catalyst. Please select one catalyst and use the thinning or thickening additive to control the viscosity.  All of the silicone additives discussed here are for use with tin catalyzed silicone where the silicone and catalyst are separate until mixing. They are not to be used with AM 125 Silicone Rubber, a 1:1 silicone where one side contains the catalyst or our platinum catalyzed silicones, like our Food Grade Silicone or our Silicone Putty.

  • Silicone Accelerator:

This silicone additive allows you to speed up the cure process from the usual 16 to 24 hours. It is added by weight to the catalyst, NOT to the white silicone base. You must use a digital gram scale for accurate weight measurement. The silicone accelerator should only be added to the catalyst at the time you are using it. The accelerator loses its potency when added to the catalyst and left to sit. It is important to remember that speeding up the cure time also shortens the pot life. So, the silicone needs to be mixed and poured in or brushed on quickly when using the accelerator. Here are some guideline weight percentages with their pot lives and cure times:

.2% by weight of accelerator to catalyst gives a 20 minute pot life and a 3 hour cure time

.6% by weight of accelerator to catalyst gives a 5 minute pot life and a 2 hour cure time

1.0 by weight of accelerator to catalyst gives a 3 minute pot life and a 1 hour cure time

You don’t want to add more than 1.0% to the mix because it can cause the finished mold to be brittle.

  • Silicone Thinner/Diluent:

The silicone thinner is added to the silicone base (part A) to decrease the viscosity of the silicone. This allows the silicone to flow more easily over intricate parts and also de-air faster. It can also be used with the brushable catalyst to achieve a thinner first coat, which reduces the chance of air bubble on the working surface of your mold. Once you add the silicone thinner to the silicone base, you weigh out the catalyst to match the weight of the silicone base and silicone thinner together. If you start with 500 grams of silicone and add 50 grams of thinner, the total weight is 550 grams and you would then add 55 grams of catalyst. You don’t want to add more than 10% silicone thinner because, while it reduces viscosity, it also reduces tensile and tear strength.

For example:

5% silicone thinner reduces viscosity by 24%, the shore hardness by 13%, the tensile strength by 13%, and the tear strength by 12%

10% silicone thinner reduces viscosity by 45%, the shore hardness by 23%, the tensile strength by 18%, and the tear strength by 16%

  • Silicone Thickener:

The silicone thickener is similar to the silicone thinner in that it is added to the silicone base (part A) to control the viscosity. The thickener is used to make a pourable silicone a brushable silicone.

To use the silicone thickener, add approximately 1% by weight to the silicone base and mix well. Again, you must use a digital gram scale in order to ensure correct weight. Add the catalyst to the TOTAL weight of the silicone base and silicone thickener. Mix well and brush on to your original. 1% is the general starting point for a brushable material. You may want to adjust up or down, depending on your application. The thickener does not affect the cure time or the durability of the finished mold.

These are the basics of working with silicone additives for tin catalyzed silicone. If you have any questions about this topic or any other, please send us an email at To see our product line and how-to videos, visit our website at









Urethane Rubber Mold for Plaster or Concrete Casting

April 17, 2017

Our 75 Shore A Urethane Rubber is a pourable material great for making molds that stand up well to repeated castings of cement, concrete, Hydrocal, plaster and other gritty and/or abrasive materials. It is a 1:1 by volume mix ratio, so no scale is needed.  For this project, I will be making a one piece block urethane rubber mold and casting in plaster.

Materials needed:

  • Original part
  • AeroMarine Products 75A Concrete Molding and Stamping Urethane Rubber with mold release (the kit comes with a silicone paste to use as a mold release)
  • Mold box (or cardboard, glue gun, and paint to make one)
  • Plastic mixing containers and plastic utensils
  • Plaster of Paris (or concrete, Hydrocal, or whatever you prefer)
  • Gloves
  • Non-sulfur modeling clay (for anchoring your original to the bottom of the mold box)

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • If you don’t have a plastic mold box, go ahead and make one from cardboard and hot glue. This post has specific details on this process,   After you have made the mold box, paint it with any paint you have laying around. I used some brown spray paint I had left over from another project and let the paint dry for several hours. The purpose of the paint is to seal the cardboard, which may have retained some atmospheric moisture. Urethane reacts poorly to even small amounts of moisture, causing bubbles and a weak finished product. Because of this, you don’t want to work with urethane on a rainy day or when the humidity is over 50% or use wood paper or waxed mixing cups and utensils.
  • Once you have the mold box made, affix some of the clay to the back of your original and press it into the bottom of the mold box. This will keep the piece from moving around during the molding process.


  • Next, use a rag or paper towel or paint brush to apply the mold release to the original and the inside of the mold box. Urethane likes to bond to most things, so we need a mold release to make sure we can remove the urethane rubber mold once it is cured.

  • Since the 75A Urethane Rubber is a 1:1 by volume mix ratio, I use plastic solo cups to measure out equal parts of the A side and the B side. Then, pour both sides into a clean plastic container and stir vigorously, taking care to scrape the sides and bottom of the mixing container. Because this product only has a 5 minute pot life, you want to mix quickly. Fortunately, it is a very low viscosity product which mixes easily.
  • Pick a corner of the mold box and pour in the urethane. Don’t pour directly on the piece.
  • Let the urethane rubber mold cure for 12 hours.
  • After 12 hours, remove the urethane rubber mold from the mold box and wash with dish soap and warm water to remove any mold release residue.

  • I’m casting with plaster of Paris, which needs to mixed 2 parts powder to 1 part water. I measure out the water and powder and then slowly add the powder to the water, stirring the whole time to avoid lumps.
  • Pour the plaster into the urethane rubber mold and let set up for 20 to 30 minutes.
  • To remove the casting, I lay a folded towel down on my work space and hold the mold over it, bending and flexing the sides until the casting pops out and lands on the towel.

That’s a urethane rubber mold and a plaster of Paris casting! You can paint the plaster casting however you choose. I’m still deciding on how I am going to paint this piece. If you have any questions about this project or others, please email us at

Make your own Silicone Soap Mold

April 3, 2017

A silicone soap mold is a fun project to do with any one or two part silicone rubber mold. Soap making supplies can be found at most craft stores (We go to Michael’s). Here, I used a rubber duck mold I had already made for another project.  If you want to make a 2 part mold, you can read the detailed post about the two part mold making process at,  If you choose to make a 1 part mold, you can read about one part block mold process, with detailed directions and a video at,

Materials needed:

  • Either an already made silicone mold or an original part (like the rubber duck I chose), sulfur free modeling clay (for a two part mold only) and a mold box.
  • Glycerin soap from a craft store
  • Glycerin soap colorant and/or scent (essential oils work well)
  • Plastic bowl and microwave to melt soap

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • Step one if you don’t have a mold is to make a mold. Please see the links above to make a one part block or two part mold. Any silicone mold can be a silicone soap mold!
  • If you have a two part mold, it must be taped together to prevent any leaking. I like to use blue painter’s tape for this. Most molds I tape in 4 strips. Make sure that the tape is holding the mold firmly together, but not so tight that it distorts the mold. You shouldn’t see any gaps and the parting line should almost be almost invisible.


  • Next, follow the directions on the glycerin soap packaging. For the soap I bought, that means chopping the block of soap into small pieces and microwaving it in 30 second increments and stirring the soap until liquid.

  • Then I added some silver metallic soap colorant and some lavender oil.

  • Pour into your silicone soap mold.

  • The glycerin soap I have says to let it set up for at least 40 minutes before demolding. Always follow the directions on the packaging for the soap you have.
  • I removed the tape and took the mold apart to reveal my silvery lavender smelling duck soap.


  • There wasn’t much flash. I easily smoothed away the little bit of flash with my finger.

There you have home made soap from a silicone soap mold. Pretty easy  to do and because the soap sets up fairly quickly, you can make many soaps from one mold in a day. If you have any questions about this project or any others, send us an email at or visit or our web site,


Trouble Shooting-Common Problems with Silicone, Latex, Urethane, Epoxy

March 23, 2017

Sometimes, when working with new materials or working familiar materials in a new way, you run into issues. We previously wrote a post about common problems with curing,   This post will focus on issues that might have a curing component (soft spots, sticky areas, etc.), but mostly on problems with the materials acting in unexpected and unwanted ways. These aren’t all the problems that could come up, only the more common problems and issues. You can always email us at if you have questions.


  • The silicone has partially cured, but is still tacky  First, make sure the silicone has had adequate time to cure by checking the cure time on the Technical Data Sheet. The Technical Data Sheet can also tell what causes cure inhibition for that silicone. Second, double check that you shook the catalyst for 60-90 seconds before measuring and mixing.  Insufficiently shaken catalyst is a very common way to get tacky silicone. Also, if it is too dry or too cold, that can cause the curing process to take longer.
  • Soft/partially cured spots  This is almost always from material that hasn’t been mixed well enough. However, if you give the silicone a few extra days, the soft spots will usually cure in the end.
  • Silicone is very brittle  Too much catalyst will make your silicone brittle. Check the Technical Data Sheet and make sure you are adding the correct amount of catalyst.
  • Air bubbles on the working surface of the mold  A few things can cause this. 1. You poured the silicone directly onto the piece. To avoid air bubbles, pick a corner of the mold box to pour and don’t pour the silicone directly on the original. 2. You poured the silicone too quickly. Pour “high and thin” as this gives the silicone time to flow around the original so pockets of air don’t get trapped. 3. There is a lot of fine detail on the original. Lots of detail gives air bubbles lots of places to cling to. Try brushing some of the silicone on the original before you pour the silicone. This method gets the silicone into crevices and helps break the surface tension that lets bubbles stick. If you are using brushable silicone and get air bubbles on the working surface of the mold, you applied the first coat too thickly. The first coat should always be the thinnest coat to ensure no air bubbles.

 Air bubbles on the working surface

  • Brushable silicone is sagging off the original The silicone has been applied too thickly. Apply the silicone more thinly, in several coats, in order to build up an appropriate mold thickness.

 Saggy silicone.

  • Silicone is sticking to the original  Silicone will chemically bond to materials that contain silica. The most common silica containing things are silicone, glass, quartz, and some pottery glazes. If you have any doubts about what your original is made of, do a small test patch on an unobtrusive area of the original piece before doing the full mold. Silicone can also mechanically bond to very porous materials. If you have a very porous original (old plaster, wood, or concrete are common porous materials), paint it first. If you don’t paint it first and the silicone sticks, patience and elbow grease can usually get the silicone off. Just peel it off very slowly to avoid damaging the original.


  • Air bubbles  It could be a few things; 1. The latex was brushed on too quickly. Slow down and brush it on your piece a little more slowly. 2. The latex was applied too thickly. Nice thin, even coats will yield the best results. 3. Using a heat gun on either too high of a setting, too closely to the mold, or holding it too long in one spot. If you are using a heat gun to speed up the dry time, use the low setting, hold the gun at least 8 inches away from the latex and keep it moving at all times.

Urethane Rubber:

  • Lots of bubbles, a foamy gray appearance  Moisture contamination. Urethane does not like contact with moisture before it’s cured. Don’t use paper, waxed or wood mixing containers or utensils and don’t mix the material on a rainy day or when the humidity is over 50%.
  • Urethane is sticking to the original or the mold box  Urethane likes to bond to most things. Check the Technical Data Sheet for a full list of what it won’t bond to. Use silicone paste (which comes with the 1/2 gallon and 2 gallon kits that we sell) or petroleum jelly on the original piece and the mold box.
  • Ripples or waves in the material or air pockets forming around the original The material is not being poured before it begins to gel. Mix and pour the urethane within 3 minutes so it has time to flow before starting to gel.
  • Soft spots  Material wasn’t mixed well enough. Don’t forget to scrape the sides and bottom of the mixing container and mix very well.

Urethane Casting Resin:

  • Bubbles, foamy appearance  Moisture contamination. Urethane does not like moisture before it’s cured. Don’t use paper, waxed or wood mixing containers or utensils and don’t mix the material on a rainy day or when the humidity is over 50%.
  • Extra Oily  Too much Part B in the mix. Make sure that you are measuring 1:1 by volume. To take care of the extra oil, dust with or submerge the part in talc, wait 12-24 hours and then wash the part with dish soap and water.
  • Soft spots  The urethane casting resin wasn’t mixed thoroughly. Don’t forget to scrape the sides and bottom of the mixing container and mix well.


  • “Oil and water” or blotchy appearance  This is usually caused by an oil based stain on the wood or actual oil stains on concrete. Try to remove all large oil stains from the concrete before applying the epoxy. If your wood is colored with an oil based stain, do thin brush coats of the epoxy, followed by a light sanding and then wipe with acetone before the next coat. Repeat these steps until the epoxy looks even.  Then, do your pour coat to the desired finish (but no more than 1/4 to a 1/2 inch at a time, depending on the surface area).
  • Lots of small bubbles  The substrate is either very porous or you are mixing with an electric or drill mixer. For porous wood or concrete, do a brush coat or two before doing the pour coat. Always mix the epoxy by hand to avoid whipping air into the mix and to avoid the friction from setting off the cure reaction early.
  • Many small or large bubbles that form about 10-20 minutes after pouring  This occurs when you pour the epoxy too thickly.  Too thick a pour will have the epoxy boiling. You can sand out all the bubbles and then do thinner pours to avoid repeating the problem.
  • Waves or ripples in the epoxy  Either the epoxy is being poured after it has started to gel or you are holding a propane torch or heat gun too close to the surface of the epoxy. Also, please remember that a hair dryer is not the same thing as a heat gun and should not be used on the epoxy because it will make waves in the epoxy. Mix the epoxy well and pour it within 5-10 minutes (quicker mixing and pouring for larger batches) to avoid the epoxy curing while you are still removing waves or ripples.
  • Epoxy cured cloudy white  The epoxy got wet while it was curing. You can sand off the white and pour or brush coat again. Always check the weather forecast before doing any outside work with the epoxy because it needs to be kept dry while curing.
  • Epoxy got super hot and cured in the mixing container  Possible causes: 1. You mixed too large a batch. 2. The ambient temperature was too high. If the temperature is over 75F, mix smaller batches than you normally would because the epoxy will cure faster as the ambient temperature increases over 75F. 3. You used a drill or electric mixer and the friction kicked off the cure process. Always mix the epoxy by hand.

These are some of the more common problems that can arise when using our products. For more information on our products, check out our website, or send us an email at


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