Most epoxy projects involve pouring epoxy onto a surface material to which it will bond. This bonding material is called a substrate. Wood is the most common substrate, though there are many others.
When epoxy attempts to bond with certain types of materials, it will first settle into any tiny grooves and pores that the material may exhibit. For this reason, we always recommend applying a seal coat to the substrate before you start pouring directly onto the surface.
In this article we'll explain the fine details behind what a seal coat is, and why it is essential for achieving the cleanest, clearest finish for your epoxy project. At the end, we'll provide a step-by-step guide to applying a seal coat to your substrate.
What is an epoxy seal coat?
A seal coat is a very thin layer of epoxy that has been applied by hand—typically with a paint brush—to a cleaned substrate to prepare it for the epoxy pouring step. The seal coat is applied using table top epoxy, as it has the necessary viscosity and curing speed to properly seal porous, uneven surfaces.
Can I use deep pour epoxy for my seal coat?
We don't recommend using deep pour epoxy for this step, because it is thinner and takes longer to cure. The thickness of table top epoxy when applied as a seal coat allows it to maintain its position even when applied to the sides of a substrate, instead of sliding downward via gravity.
Why is a seal coat so important?
Many materials used as a substrate for epoxy are porous. Sometimes these pores are easy to see, but often they are too small. Still, their presence is a concern because each pore can hold a tiny amount of air or moisture that will negatively affect the epoxy resin's ability to bond firmly with the substrate.
A seal coat of epoxy will seep into the surface level pores of the substrate and release or trap the air within, preventing it from interfering with the bonding process of your flood coat or deep coat, as well as greatly reducing the number of air bubbles you may have to deal with.
When you later pour your flood coat (or deep coat if you're also using deep pour epoxy), you can expect the strong, resilient bond that epoxy is known for.
Is one seal coat enough?
For many cases, a single seal coat will be sufficient. If you have an obviously porous wood, or if you're simply not sure, you can apply a second and even a third final seal coat, four hours after each previous one.
After my seal coat, when should I pour my flood coat or deep pour coat?
The seal coat will begin to cure several minutes after you've mixed it. For the next twelve hours it will become tacky, a phase it enters as it continues to harden.
We recommend mixing and pouring your flood or deep pour coat four hours after you apply your seal coats. The epoxy will mesh nicely with the stickiness of the seal coat at that point.
What if I forgot the seal coat and have already poured my epoxy?
If you've poured your epoxy without a seal coat, numerous tiny air bubbles may be released from the substrate and get stuck within the thick flood coat or deep pour coat. Very porous substrates may even absorb some of the epoxy after you finish pouring, leaving your coat uneven in different locations.
How do I remove air bubbles from the epoxy?
To remove air bubbles, use a heat gun or propane torch to burst them. The air will leave the epoxy, and if done soon enough (within 15-20 minutes of pouring), the epoxy should continue to self-level into a smooth coat like normal. Propane torches are very effective at this, but require a bit of focus and precision.
If you use a propane torch to remove bubbles, you must keep the flame at a distance and keep it moving constantly. Don't let the flame touch the epoxy at all, and don't hold it over any particular spot for more than a full second, as this is the point at which it may cause heat damage to the epoxy.
I brushed on a seal coat, but the brush left behind stroke marks. What can I do?
This is normal. Once you've applied your flood coat or deep pour coat, the brush strokes will vanish as the new epoxy meshes with the seal coat to essentially become one thick layer. These strokes will no longer be present
As long as you follow the instructions that are intended for your brand of epoxy, it should result in a transparent glasslike finish. However, we can only guarantee the quality of our own UltraClear brand of epoxy. If you're using our table top epoxy brand, you can find a detailed set of instructions here for the entire epoxy process here.
What supplies do I need to apply a seal coat?
Aside from the table top epoxy itself, you'll need the following for your seal coat:
- Stir sticks - These are necessary for mixing small batches of epoxy. We recommend mixing batches of 32 oz total (or less as needed) for your seal coat, so that you have enough time to apply the mixed resin before it starts to harden. You can mix additional batches afterward as needed until your seal coat is complete.
- A mixing container - For each seal coat, you'll want a small clean container to mix your epoxy components in. We suggest quart-sized containers with measurement lines, so you can accurately add the exact amount of each component into the mix. For example, our UltraClear Table Top Epoxy has a 1:1 mixture, so to create 32 oz of epoxy, you'd mix 16 oz of the resin component with 16 oz of the hardener.
- A paint brush - Use a new or clean brush that won't lose bristles as you apply the epoxy. Lost bristles can become stuck in the epoxy and may be difficult to remove if not noticed in time.
You can find these supplies on our website or at most home improvement stores.
Our step-by-step guide to applying a seal coat
As with any epoxy project, make sure you have all the necessary supplies and a properly prepared working environment before you begin. Then follow the steps below:
Measuring your epoxy - To start, add your epoxy resin component into the container you'll be using to mix. Then add your hardener component. The amount you'll need may vary, but usually 32 oz total is more than enough. If you feel like you'll need more time, start with a smaller batch. You can always mix more after brushing until your entire substrate is sealed. Be sure to use a clean container for each new batch.
Our table top epoxy uses a 1:1 ratio, so a 32 oz measurement would be 16 oz of resin and 16 oz of hardener.
For a seal coat, don't mix more than 32 oz total at a time. If you'll need more than 32 oz, you should mix the extra amount as a second batch immediately after you finish brushing on the first batch.
Mixing your epoxy - Use your stir sticks to mix the components thoroughly, being sure to scrape the sides and bottom so that everything is mixed well. Mix it for a total of two to three minutes.
Note: after mixing, it's possible that a small amount of epoxy will stick to the sides; this is common and not a cause for concern. Don't attempt to scrape off or use that sticky residue, as it is just remnants of components that weren't fully mixed and won't cure properly.
- Applying the seal coat - Immediately begin brushing your epoxy mix onto the surface of your substrate. Make sure to cover any nooks or grooves that may be present, such as on objects with unconventional or rougher shapes.
- Wait four hours - After you finish brushing on the seal coat, you'll need to wait four hours for it to partially cure. The seal coat will become tacky and be ready for either a second seal coat, your flood coat, or your deep pour coat if you're also using deep pour epoxy.
And that's how you apply a seal coat. The next step will be pouring a flood coat or deep pour coat, depending on your project goals.
Have questions or want assistance? Let us know!
Epoxy projects can seem like a big undertaking. If you're unsure about any part of the process, or if you would like help planning your project, you can reach out to us through email or phone here, or talk to one of our experts through our text chat support by clicking the help button at the bottom right of your screen.