What happens when you cut epoxy 50 percent with acetone?

I don't normally thin epoxy unless I'm injecting it with a syringe or really need it to soak into a porous material, but I never did a side-by-side comparison of thinned vs. un-thinned epoxy. This test answered some of my own questions, and hopefully some of yours as well.

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[robertschulke]

25 years of wooden boat ownership, repair, and research here. Thinning epoxy with acetone has a few effects.
1 - It does not help with penetration. The acetone penetrates easily into the wood, but the larger epoxy molecules penetrate much less. If you want epoxy to penetrate wood, use a low viscosity or penetrating epoxy such as MAS. Another approach is to preheat the wood to the desired depth, but this will cause the epoxy to set much faster.
2 - The acetone as you noted will outgas through the epoxy leaving bubbles and porosity all the way through it. This makes it permeable to air and water.
3 - Any chemical, e.g. acetone, added to epoxy will change the chemistry. In this case, it retarded the resin/hardener curing reaction. It likely affected the strength as well.
A side note: heat, such as a heat gun or a judiciously applied propane torch, will help the epoxy flow out and eliminate bubbles. This is a standard technique on epoxy countertops and floors.

[zakaroonetwork]

Denatured Alcohol is recommended for thinning of epoxy. Acetone will interfere with polymer cross linking. That is why we use Acetone for Epoxy clean up.

[philip]

To remove the bubbles in the surface of the epoxy just lightly spray with alcohol.
This removes the surface tension and allows the bubbles to escape.

[classicbob]

42 years ago we also used the 50/50 process to put a finish on our wood race boats. We would sand the first coat after a few days and then apply a second coat. It made the boat look like a piece of furniture. Fast forward to today and the wood finish still looks good and the wood was protected from the water.

[freedom_aint_free]

1) Acetone is hygroscopic, e.g. it attracts water;
2) Acetone can also react with epoxy catalysts that are usually some kind of amine;
You should try for instance, xylene or ethyl acetate that will dissolve similar things that acetone does but are way less reactive.

[delmarrey]

As a retired boat builder I used 10% MEK to mixed epoxy for the first coat over wood with fiberglass, or to bond 2 pieces of wood together. This allows the epoxy to soak deeper into the wood for adhesion. Then the next coats with fiberglass would be 100% epoxy. MEK evaporates faster then acetone, which allows for a faster cure.

[stankrajewski]

I am a woodworker and wooden boat restorer. I start my outdoor and boat wood with Smith's Clear Penetrating Epoxy Sealer (CPES). This is "high octane" stuff--I wear an OGV-HEPA full face respirator when applying it, but it penetrates wood like no other thinned epoxy that I have used. In the world of composite hulls (wood and ply "sealed" with epoxy), boat builders rely on thicker and thicker epoxy to create ugly dense plastic boats that offend the wooden bones that lie underneath. My journey is not complete--more field tests will reveal more findings--but old boats will tell you a lot if you are listening.

[camike]

I use Acetone for thinning epoxy resin when have to brush it over non flat surface. Like round ones from wood lathe. But very little. maybe 1 to 15 proportion or maybe even less. Just eyeballing. It does takes longer to cure, but surface is thin, even and glass like. I also leave it in the lathe, slow spinning to keep it even spread until it starts hardening. It will cure faster, if heat it up a little, time to time with a heat gun. Don't overheat it.

[TTM-GEB]

Awsome experiment - Totally explains why I found a completely cured but very flexible leftover in the bottom of my mixing cup that I must have put some acetone in after cleaning a brush maybe 😊

[elzamiller]

Thank you. I'm just getting into epoxy reason and I've been curious about the thinning of it. I'll stay with full strength.

[vitsirosh]

So happy you did this test for us. Always wondered. Thanks a bunch

[wileycoyotesr]

Fascinating. Who would have thought diluted epoxy wouldn't be strong as that which was engineered for high impact resistance. I wonder what would happen if you made two batches of pancake mix under similar conditions? The possibility of various test subjects is limitless. Keep these tests coming. 👍👍👍

[paddiman]

A number of years ago, I was doing some laminating with epoxy. Yes, you can thin epoxies with Acetone. But very little is required. Also, there are many diff. kinds of epoxy. I preferred using some with sufficient pot life (45-90min) to tack. The trouble with mixing anything with epoxy is the act of trapping air into the mixture. So I used specially modified mixing machine to accomplish this. Worked very well. But I also added another aspect to the process using vacuum to remove unwanted air bubbles from the epoxy being poured.
Acetone is generally used to flash air bubbles from a poured surface using spray bottle. When the exotherms kick in the cure progresses. But thinning the typical, 2-part epoxies affects both cure times and final results, as well as durability. Compounding anything into epoxy during mixing traps air. So the more mixing you do makes it worse. And thinning with any solvent only degrades the balance between the amines and hardener. As I recall, I used approx. 10% Acetone. Then I mixed my compound in a vacuum environment. I could tell you more. But am reluctant to do so on this platform.

[salvagedsteelstudio]

Legend has it, the thinned down epoxy is still curing to this day..

[chriswhitman]

I make wooden fishing lures and many people recommend using polyurethane or super glue to waterproof the lures before painting. My preferred form of waterproofing is mixing devcon 2 ton epoxy with a few drops of acetone to make it very thin, then painting the lure with it. It not only makes it waterproof but causes the outer layer to become much more durable. I've found the lures resist dents and abrasions better.

[randyc]

When the epoxy has flowed out but still liquid, try a hair dryer, heat gun or propane torch with a fan nozzle to draw out the bubbles. Practice a little.

[leebonifay]

The container of acetone will tell you that thinning at over 10% will cause curing and strength issues. Using TWO coats of acetone-thinned epoxy (while running through a strainer to take out the bubbles) will give you a rock solid coating that looks like glass.

[azalea_moon-kee]

The MEK comments are really good; it's about the chemistry..."You have to respect the chemistry, Jesse." The only other suggestion would be to make a ghetto vacuum chamber using one of the shop buckets from home Depot or Lowe's and then fit your Shop-Vac to it.

[GrantOakes]

Since acetone is used for cleaning up brushes and rollers after layups since it completely dissolves epoxy, I would imagine it significantly degrades epoxy in ANY dilution! I personally wouldn't put even 10% acetone to my epoxy. If all you want it to seal in wood just go with polyurethane.

[Suntanned]

I was curious about this, thank you for making this video