Exposure test of wood coatings

[rxc463]

I ran across this page when looking for info on RAKA products. Gives application and performance info and pics on several well known finishes.
It was a little eye opening to me, but then I have always been partial to paint finishes. This is new to me, so sorry if this link has been posted before.

http://www.mar-k.com/final_summary.html

[Miriam C.]

I can tell you from experience Helmsman spar urethane isn't the best. CPES and epoxy only water proofs. You still need to keep the UV damage from happening.

[Steve_Cox]

I ran across this page when looking for info on RAKA products. Gives application and performance info and pics on several well known finishes.
It was a little eye opening to me, but then I have always been partial to paint finishes. This is new to me, so sorry if this link has been posted before.

http://www.mar-k.com/final_summary.html

Good link, thanks

"3. Pine seems to be more resistant to weather damage than oak."

Seemed odd, but I would guess it absorbs the coatings better than hardwood. Also I didn't know POR15 was used on wood, berry interesting

[Nitetimes]

I ran across this page when looking for info on RAKA products. Gives application and performance info and pics on several well known finishes.
It was a little eye opening to me, but then I have always been partial to paint finishes. This is new to me, so sorry if this link has been posted before.

http://www.mar-k.com/final_summary.html

Good link, thanks

"3. Pine seems to be more resistant to weather damage than oak."

Seemed odd, but I would guess it absorbs the coatings better than hardwood. Also I didn't know POR15 was used on wood, berry interesting

If I'm not mistaken (it happens) pine has more oils in it than oak, could have something to do with it.

[Arne]

I will pass this along a personal opinion. one of the areas of a tear that seems particularly susceptible to water infiltration is the bottom of the walls. The water rolls down the sides and hangs on the bottom of the wall. If there is any opening, the water will be sucked into the wood by capillary action.
I've even seen this on the older camp-inns with wooden sides.

The trick, for me, is to make the side continue down by caulking between the frame and wall. That way, the water continues from the wall, over the caulk and on to the frame, where it can sit or drip off.

I also heavily cpes the wall and especially the edges, then paint the tear.. but the last thing I do is caulk the seam between the wall and frame, so the water will not sit on the bottom of the wall.

On mine, where the wall does not have a frame under it, I still rub caulk on the wall bottom to help seal it.

pages 11 & 12 have a couple of pix... I tape it to get a clean fill, then caulk, then paint over it.. the paint covers wall and caulk seam.... should last for years.

[S. Heisley]

If a test is going to be fair and equal, the same number of coats should be applied in all instances. While topcoats were applied 3 times in all tests, the primers were not applied in equal amounts. This can disrupt/sway the results considerably. The following extracted information excludes the two worst, Glisten and Linseed Oil:

PRIMER NAME # COATS APPLIED

Pelucid 3
PQR-15 3
RAKA 2
CPES 1

The selections with 3 coats of primer applied (Pelucid or PQR-15) were considered the best performers. Perhaps, if the other primers had been applied 3 times, we would have seen a good to excellent result with those as well.

[S. Heisley]

Steve Cox wrote:

"3. Pine seems to be more resistant to weather damage than oak."

Seemed odd, but I would guess it absorbs the coatings better than hardwood. Also I didn't know POR15 was used on wood

I question this finding on the oak. If you eliminate the two worst finish performers, #8 and #10 (both Oak based), you will see that Oak didn't do so bad. However, I think the deciding factor in these tests may be the number of coats of primer (again, excluding Glisten & Linseed oil) used. I may be wrong; but, here's what I extracted from Mar-K's findings:

Item#...Wood...#Primer coats/#Finish coats...Surmised Rating

#1...Oak...1/3...Needed more Primer?
#2...Pine...1/3...Needed more Primer?
#3...Oak...2/3...Jury's Out
#4...Oak...1/3...Did Okay
#5...Oak...2/3...Did Okay
#6...Oak...3/3...Most Durable Clear Finish
#7...Oak...3/3...Best Overall Finish
#9...Pine...3/3...Best Clear Finish

Again, please look at the amount of primer used. Unless I goofed, it looks like Oak didn't do so bad.

[Steve_Cox]

Sharon,

You are a wise woman, I on the other hand just looked at the pictures

[doug hodder]

I wonder if they had coated the underside or just left it raw wood, didn't see it when I read the info on it, maybe I missed that. On a boat, you coat the hull both inside and out to prevent moisture from getting under the exterior finish. While the top coat protects that surface, moisture can come in from an uncoated side and help lift the top coat if not encapsulated. Doug

[S. Heisley]

While the top coat protects that surface, moisture can come in from an uncoated side and help lift the top coat if not encapsulated. Doug

...Good Point!

[angib]

The most significant finding of that test is that it is the preparation and protection of the end grain that matters - there are just so many variables about how the samples were prepared that I'm not sure it tells us all that much - were the backs coated, were the concealed sides coated, how well was the end grain coated?

Unless they've been 'trained', I've never seen a novice that can feed enough epoxy into end grain - this has to be repeated over and over again until the epoxy starts to gel - a single coat will wick up the end grain, making it 'epoxy-dampened' not 'epoxy-soaked', so it will not be an effective barrier to moisture.

And as I've mentioned here before, my training was the exact opposite of what many here say - I learnt to never, ever thin epoxy - where the thinners evaporates, it will leave voids that moisture can pass through. A fairly thin layer that's 100% epoxy-soaked is much more resistant to moisture than a deep porous layer.

Andrew