Thread: Another epoxy question

What about if the coat is on another coat of epoxy, not the wood? Is it then safe to use alcohol or mineral spirits?

Uh... if you are coating epoxy with more epoxy, you ARE scuff sanding the first coat, right? Otherwise you WILL have issues. And I'll second the use of a faster evaporating solvent such as acetone as mentioned above... I suggested mineral spirits with a longer drying period as it tends to flush contaminants out of raw wood better, but nothing is perfect. I actually keep a can of R/C modeling "dope thinner" around for when I need to degrease quickly. Lacquer thinner works the same.

Christian

Originally Posted by kaptain_zero

Uh... if you are coating epoxy with more epoxy, you ARE scuff sanding the first coat, right?

Yup. I learned a long time ago to rough up the surface before applying anything like an adhesive.

If you are using a finish that is thermosetting like epoxy, CA, or varnish it is important to scuff between coats. With finishes like that, there is a mechanical bond between the coats and scuffing the surface increases the surface area and promotes better bonding. Scuffing is not always necessary if the prior coats are not fully cured. They do not melt into each other like a lacquer or shellac would do.

The reasoning for the two solvents (like mineral spirits and acetone) is that they have different solubility parameters. Between the two of them, they will get the most common contaminants. Odorless mineral spirits can be slow to dry but regular mineral spirits and especially naptha evaporate quicker.

Alcohol will absorb some water out of the air and cause some grain raising, but in my experience this is mostly theoretical and does not happen to a great degree.

Charlie

Just wanna say thanks to everyone who helped here. I started wiping down the scales with mineral spirits before a pour and that seemed to work. I guess it was a contaimination issue that caused the voids. Now I can finally get those damn near flawless epoxy pours

If you're cleaning up epoxy, denatured alcohol is a good choice, as well as acetone. Just don't soak it too much in the acetone.

If you can't vacuum the scales while it cures (which is going to be the best way), you can also vacuum the resin. Just mix it up properly, put it in a proper container, and set a vacuum to it. You can suck excess air out that way, then use an acid brush to brush the resin on. Finish sand it with a high grit paper and you're good to go!

I tried to find the vacuum pumps, but to no avail. They're affectionately called "pucks" by composite guys, but they're small disks of metal that connect straight to an air compressor and provide good vacuum pressure (45 psi if I remember right). You get that, some non-stick vacuum bagging, and you're on your way to easy vacuums and high pressure.