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What is the best kind of epoxy resin to use?

November 19, 2021

One of the most common questions we get about epoxy is, “what kind of epoxy do I need for my project?”  This is a question that has more depth and nuance than one might first expect.  The first thing you must consider is what is your project, and what do you need it to do?  Once you have that you can figure out what kind of epoxy you’ll need, but first a quick tutorial on how epoxy works and the ins and outs of epoxy.

To start with, epoxy is a type of polymer that uses heat to become the hard plastic you might be familiar with.  2 part epoxies have, well, two parts- the resin and hardener.  Once the hardener is added to the resin a reaction kicks off that starts creating a lot of heat, which leads to hard plastic.  The heat is important to take note of because more epoxy in a volume will result in more heat being produced.  The amount of heat being produced can have a significant impact on how you use the epoxy.

Epoxy excels in projects where you need clarity and long-lasting durability.  Whether that is creating a beach scene in a diorama or coating a wood countertop to make sure the natural beauty of the wood shines through while being well protected from moisture and physical damage alike.  Spreading layers of epoxy over an area is called Laminating, which is where laminating epoxies like AeroMarine Products 300/21 system excels.

So if your project has you spreading thin layers of epoxy, not more than ¼ inch (about 6mm) in depth over a large area, or you’re using a cloth like fiberglass, carbon fiber, or aramid, what you’ll want to use is AeroMarine Products 300/21 laminating epoxy.

Laminating epoxy is also very useful with pebble paving.  Using a low viscosity epoxy that can get between the pebbles and reinforce the bonds between the pebbles and concrete substrate and can be vital to making sure that your pebbles stay where you want them instead of coming out and getting under foot.  Getting a low viscosity epoxy that also becomes glass-like in glossiness when it cures means not only will your pebbles stay in place, but it will regain its like-new shine as well.  In all of these applications, AeroMarine Products 300/21 Rock and Pebble Epoxy is an ideal choice for both the DIY-er and professional.

The other type of epoxy that is widely available is Deep Pour Epoxy.  This type of epoxy also cures clear and hard like laminating epoxy, but does so while generating a lot less heat so it doesn’t risk boiling and leaving unsightly voids in your piece.  Deep Pour epoxy is usually a bit thicker than laminating epoxy, so it’s not as useful for things involving fiberglass, carbon fiber, or aramid, but when it comes to filling a volume with clear and durable epoxy it can’t be beat. Unfortunately we don’t currently sell a Deep Pour epoxy, but keep your eye out for new products in the future!

As impressive as epoxy is, it’s not going to be a great fit for all projects.  Depending on the materials used in the project the epoxy may not be able to stick and can leave you in a bad place.  Let’s look at a couple common culprits:

First are polypropylene and polyethylene plastics.  These are commonly used plastics in consumer goods, such as plastic drink bottles, plastic trash bags, plastic food containers, or even clear plastic packing tape.  They are inexpensive forms of plastic and are easily used in manufacturing, making them common in inexpensive consumer goods.  Projects making extensive use of polyethylene or polypropylene plastics, however, should look for a different resin as epoxy won’t stick to either of these types of plastic.  The good news is that you can take advantage of this lack of adhesion for places where you don’t want epoxy to stick such as in a mold box for a resin river table.

The next material to be wary of is Anodized Aluminum.  Anodized aluminum is much more colorful and has a harder surface finish than raw aluminum, but epoxy has trouble bonding to it.  The reason for this is that the surface of anodized aluminum is covered in microscopic pits, where the pigment molecules attach and give the surface its color.  These pits where the pigments reside are also where the epoxy wants to adhere, and the pigment prevents the epoxy from sticking very well.  So if you’re doing a project with anodized aluminum and want to coat or embed it in epoxy you’ll need to find a different resin to use.

Fun fact: the size of those microscopic pits are also what limits the range of colors you can get through anodization as some pigment molecules are just too big to fit in them.

Next we have galvanized metals.  Iron and steel can be galvanized either by electrochemical plating or just dipping the piece in a bath of hot liquid zinc metal.  As the zinc cools, the surface of the piece gets covered in a layer of zinc carbonate.  This gives the metal part excellent resistance to corrosion and rust but interferes with the ability of epoxy to adhere to it.  Most epoxies can’t adhere to zinc, so if you’re working with galvanized metal you’ll need to carefully remove the zinc layer first.

The last thing to cover is going to be the presence of oils and petroleum products on the surface of the piece you want to use epoxy on.  Simply put epoxy does not work well with oils, petroleum or otherwise.  Cedar oil, tung oil, linseed oil, motor oil, bitumen – all of these will cause adhesion problems for epoxy.  For surfaces like tabletops or garage floors, the presence of oil will cause patches where the epoxy retreats and doesn’t cover, leading to an undesirable “orange peel” or “fisheye” effect.  In some cases, trying to use epoxy pebble paving on asphalt driveways can result in entire chunks of the surface delaminating and coming off entirely.  We emphatically recommend against using pebble paving over asphalt substrate.

While tabletops and countertops can be cleaned with acetone to mitigate the impact of oils on the epoxy layer, the best way to handle it is to either avoid using oily woods, oily stains, or use a different resin.

That should about wrap it up and as always if you have any questions about your project and what you need for it don’t hesitate to contact us by email, contact form, or phone during our working hours.  We look forward to hearing from you!

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