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Sealing Wood - Experiments - Test Results

Penetrating Epoxies - Test Results (background info)

Copper Filler for Epoxies - Similar Test Results

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Paul Oman, MS, MBA - Progressive Epoxy Polymers, Inc.

Member: NACE (National Assoc. of Corrosion Engineers), SSPC (Soc. of Protective Coatings)

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02/02

Common wisdom is that the best way to seal wood (and probably concrete) is with a coat of thinned (penetrating) or perhaps unthinned epoxy. I recently decided to test this and the results were surprising.

I began with four blocks of wood cut from a piece of new, cheap pine. Each block was about 3/4 wide and 2 by 2.5 inches square. One block was left uncoated, one was coated with one coat of our Low V (low viscosity) epoxy, one was covered with one coat of Low V epoxy solvent thinned 15-20%, and the last block was coated with one coat of our Aluthane moisture cured urethane primer and topcoat. After coating the samples were allowed to cure for 36 hours and then submerged in water for 5 days. There are the results:

plain uncoated block gained 52% in weight

unthinned epoxy coated block gained 17% in weight

thinned epoxy coated block gained 20% in weight

the aluthane coated block gained 9.5% in weight

The experiment was then repeated using a 3 blocks cut from a new 2 by 4. One block was left blank, one block was coated with aluthane and the last block was coated with our water based fluoro polymer. After coating, the blocks were allowed to dry for 30 hours and then submerged in water for days. The results:

untreated block = weight gain was 35%

fluoro polymer treated block = weight gain was 25%

Aluthane urethane coated block = 14%

Same test. Small wooden blocks coated, allowed to cure for 24 plus hours, then soaked in water for several days.

uncoat block = 19 grams went to 28 grams = 47% increase

block coated with Low V epoxy = 22 grams went to 27 grams = 23% increase

block coated with Aluthene urethane primer = 21 grams went to 22 grams = 5% increase

block coated with "Product X" = 21 grams went to 27 grams = 28.5% increase

MORE TESTS WITH Product X - SEE OCT 27, 2002 TESTS

Same test. Small wooden blocks coated, allowed to cure for 24 plus hours, then soaked in water for several days.

uncoated block = 65% weight gain

blocked coated with a one part urethane clearcoat = 31% weight gain

block coated with two coats of one part urethane clearcoat = 24% weight gain

block coated with one coat of Aluthane primer = 16% weight gain

block coatd with two coats of Aluthane primer = 6% weight gain

I was surprised that epoxies didn't seal as well as I thought they would. I imagine that two coats - or a thicker single coat - of epoxy is needed over raw wood to really seal it well. The Low V epoxy I used in these tests is our low viscosity epoxy. Thinning the epoxy with solvents (making it a 'penetrating' epoxy) lowered the performance of the epoxy even more.

I was also surprised at the excellent performance of our Aluthane primer. Even better with two coats (test #4) I only included it in the first round of tests on a lark. We only carry the Aluthane cause generally you want an epoxy or some sort of primer under the 2-part polyurethanes we carry and also because the Aluthane, if used as a topcoat, gives a neat fresh galvanized look to surfaces (such as trailers, sailboat masts, etc). If you get aluthane on your hands it doesn't come off. Never seen and epoxy or paint that was that difficult to remove (guess that's good for a primer!). Also if you get aluthane in the rim of your paint can (or on the threads if you store the excess in a jar), you'll never get the lid off. I never used any product that was that bad about 'gluing' the lid up so completely (again, probably a good thing). Note that Aluthane contains plenty of solvent and is rather smelly to work with. We sell it for $26 quart. It's very thin and a quart will cover about 100 square feet.

I am currently in the process of building a stitch and glue canoe. Based on these tests I will prime the plywood with Aluthane before painting. I also have a dark green fiberglass canoe/kayak that I painted the interior of with Aluthane because I liked the semi-shiny, bright silver look to the very dark green (pigmented resin???) fiberglass weave inside.

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Additional testing (5/27/02)

I have been evaluating a water based epoxy and thought I would see how well it worked as a wood sealer. Same sort of test - coat wood, soak for several days, measure increase in weight....

block 1 - uncoated wood - weight gain 40%

block 2 - one coat aluthane - gain 21%

block 3 - two coats aluthane - gain 0%

block 4 - one coat water based epoxy - gain 25%

block 5 - two coats of water based epoxy - gain 8%

block 6 - one coat of Low V epoxy - gain 16%

block 7 - two coats of Low V epoxy - gain 4%

LOOKS LIKE YOU SHOULD ALWAYS SEAL WITH TWO COATS!!!!!

10/21/02

Test of a solvent-based epoxy

tesing using a thickish, pigmented, solvent based epoxy vs the Low V epoxy. Two blocks coated with the Low V epoxy - average weight gain was 10%. With the solvent based epoxy gain was 9%. Uncoated control block gained 31%.

10/27/02

Test of our new solvent based penetrating epoxy (ESP 155) which is approx. 25% solvent and 75% epoxy, vs Product X brand penetrating epoxy (which is approximately 70% solvent and 30% epoxy).

Note: see our comments on solvent vs. epoxy concentrations in penetrating epoxies see http://www.epoxyproducts.com/penetrating4u.html

For list of solvents see http://www.epoxyproducts.com/solvents.html

there are legal limits to the amount of solvents that can be used in these products - see http://www.epoxyproducts.com/voc.html

Blocks were cut from a 2 X 3 so the two major block faces were 'end-grain' and thus extremely porous.

On the ESP blocks there was an epoxy shine on the wood even after just one coat. The Product X blocks exhibited no epoxy shine even after two coats. (EPS 155 - Epoxy Sealer & Primer - now available from Progressive Epoxy Polymers, Inc. http://www.epoxyproducts.com)

block 1 - no coating just the raw wood, initial weight 24 grams, after several days of water soaking weight increased to 38 grams - total gain 58%.

block 2 - block coated with one coat of Product X - initial 23 grams, final 33 grams, gain = 43%

block 3 - block coated with two coats of Product X - initial 24 grams, final 31 grams, gain = 29%

block 4 - block coated with one coat of ESP - initial 28 grams, final 29 grams, gain = 3.5%

block 5 - block coated with two coats of ESP - initial 28 grams, final 29 grams, gain 3.5%

Observations/thoughts: On really porous surfaces one needs a good deal of epoxy to seal the wood and not simply penetrate and evaporate away. It would appear that the multiple coats of Product X were heading in the right direction as more and more epoxy was being deposited with each coat. The ESP, with 75% epoxy, sealed completely in just one coat. It would appear that it would much more than 3 coats of Product X to seal as well as the higher epoxy concentrated ESP epoxy. Note that both Product X and ESP have the same watery viscosity. Product X is more expensive (gallon vs gallon price) and requires several more coats to obtain the same degree of sealing (or priming). Click here for "solvents used by product".

june 2004 - another test

Tested our Epoxy Primer™ product which is especially formulated for use.

25 gram block coated once and submerged several days - final weight 26 grams

more on this product:

(find in marine catalog - section 4 EPOXYPAINT) or (find in our industrial catalog - section A EPOXYPAINT). This primer/penetrating epoxy is only 15 percent solvent (85% epoxy) - however it seals and primers extremely well for several reasons: 1) It contains what our formulators call a bond enhancer - actually it's something that reduces surface tension so the product is drawn into the porous surface better (as if it had a higher solvent percentage); 2) It contains a large amount of white pigment. This makes it very useful as an undercoat primer so that less topcoats are needed to get a uniform topcoat color and the pigments also 'plug' surface pores and irregularies this improving surface sealing; 3) it uses moisture tolerant resins/curing agents so that it bonds to damp surfaces; 4) it is a simple 1 to 1 mix with a long potlife. ---- OUR BEST SOLUTION FOR A PIGMENTED PRIMER AND SEALER!!! If you need CLEAR such as under vanish etc. we recommend our ESP 155™ (find in marine catalog - section 1 MARINERESINS) or (find in our industrial catalog - section D CLEAR EPOXIES) EPOXYPAINT)

LEGAL NOTICE: There are federal, state and sometimes county restrictions for the use of solvents. High solvent products are generally illegal throughout the entire USA. The 'fix' by these vendors is to use some 'low end (???)' solvents that are excempt from the regulations. So, instead of a good product, you might just be getting a 'legal' product. For details on VOC (solvent) restrictions see: http://www.epoxyproducts.com/voc.html. Note that if you add solvents to products and thus exceed the VOC regulations in your area, you are technically breaking the law.

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Goto our 1-line product/price summary page MARINE or INDUSTRIAL

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