I made an epoxy fill in a tabletop. I used a heat gun to remove bubbles. I still got bubbles on the edges. I saw a YouTube video from blacktail studio about deep pour epoxy table tops where the presentor suggested sealing the wood edges with shellac to prevent air coming up from the wood. I think my bubbles came from the wood that I did not seal.
I am going to leave it alone but do you think it came from the wood?
I’ve been researching this as well and I would 99% say that it’s from the unsealed wood. also if you’re using a colored epoxy you need to seal all the surfaces of the wood with clear epoxy to prevent bleeding (what i’ve seen as the best method) and let dry for 24 hrs min, some have had good success with fast setting epoxy to reduce that time.
you might be able to fill those holes with black starbond fill/CA glue
Air can definitely come up from the wood.
I just epoxy filled some through mortises in dining benches I made and on the first bench, to my newbieness, I thought, “more heat, more better” and realized that there was a point that I could heat the area up to where air bubbles would start forming in the pattern of the end grain. I didn’t make the same mistake on the second bench but since I had poured both benches at the same time, I couldn’t seal the wood beforehand.
Heat is generally used to thin epoxy without altering solids content, and as a method of breaking surface tension. Additionally, the chemical process is exothermic. Both introduce some degree of heat into the media. When presenting a porous media with a temperature increase, outgassing will occur.
Simple solution is to pre seal or preheat the media, or a combination of both. Additionally, dependent on system and ambient, the epoxy system can be preheated for a seal coat. By preheating media and epoxy, you will get maximal penetration without porosity.
The last epoxy project I did before this I forgot to get the heat gun out. I had bubbles in the middle of an area and not around the edges. I had sealed that project with shellac. This project I guess I got excited and skipped the shellac and got the bubbles around the edges and no bubbles in the middle of the pours. I guess it is just live and learn. I have been watching several people on youtube about deep pour epoxy projects and there is a lot to learn.
sealing the wood will help… but there is another thing that makes a huge difference: Heating up the epoxy components before you mix them… to 75F to 80F.
And also keep it heated during mixing (I use a pretty cheap USB coffee cup heater from Amazon for this)
Warm epoxy has a much higher viscosity (closer to water) and also seems to be more willing to let bubbles in it go to the top quickly (where the heatgun makes quick work of them)
Second thing is that I tend to do the heatgun multiple times, about every 5 minutes for the first 25
NOTE: Warm epoxy will cure a bit quicker so this may reduce your working time a bit
Wouldn’t this be a lower viscosity?
Yes. Heating epoxy thins it. You will often see people using volatile solvents to thin epoxy, some systems even use this methodology, especially with some “penetrating” epoxies. This is not sound methodology, and largely defeats the advantages epoxy has over other systems. The solvent, by way of evaporation, introduces porosity.
You will introduce bubbles when mixing, the degree of which will be related to viscosity of the system and the action you impart. I do a lot of cold molding, and when I am applying a finish coat to a raw carbon part or something to fill the weave, I put the resin under a vacuum to degas it. Brush, roller, pour ect will introduce air too. You can bag your part as well.
I rarely use a heat gun to burst bubbles. There are a lot of tricks. I’ll refrain from suggesting anything in particular, I’ve poisoned myself plenty. But if you consult your systems formulator, I imagine they will offer some solutions.
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