Varnish over CPES Problems

[E. Kelliher]

This summer I had the teak on my Cape Dory 36 stripped and replaced with 2 coats of Smith & Co. CPES and 6 coats of Interlux Goldspar 95 High Gloss Ployurethane Varnish. The job was completed 4 weeks ago. There are now what look like teak oxidation sploches appearing on the toe rail. I believe all of the CPEs and varnish manifacture's directions were followed. Does anyone have any ideas on what the problem could be?

[Ian McColgin]

One possibility is that for some reason the CPES did not take well to the teak. Of all the epoxies, CPES has been the friendliest, in my experience, to teak but you could still easily leave enough oils at the surface to make a problem.

I personally like teak either oiled or allowed to silver and find that much less trouble anyway. I usually let boat owners find another contractor if they really want it finished bright.

Another likely sourse of trouble, endemic to toe rails, is moisture coming up and getting trapped under the varnish, which is not vapor permiable. Especially if the problem is most prevalent around bungs or around places along the innter edge of the toerail that look like moisture might lie in that corner, I'd give this my first guess.

If that's it, best course is to go all vapor permiable by putting a water based finish like CETOL on top.

Again, I wonder at why all the effort. CETOL by itself makes a very good finish that is easily touched up year to year. A really good job of CPES under CETOL on teak will look good but takes as many coats of CETOL to get the effect as CETOL alone. CPES&CETOL will last quite a while but when (not if) it goes, it's real work to fix.

[paladin]

did you clean the teak first....before using CPES on the teak it should have been wiped down with a cloth and acetone, allowed to dry well, then re-clean again with the acetone to make sure as much surface oil as possible is removed...THEN on goes the CPES and usually only one coat, and if it looks glossy anywhere you should use 400 grit to remove the gloss....then your varnish......but then again.....I also prefer the oil.....

[Bob Smalser]

...teak oxidation sploches... Sure it's not just salt that wasn't cleaned thoroughly?

Some woods are also full of natural salts fromthe soil they grew in that appears without warning beneath a finish.

[Wild Wassa]

Originally posted by E. Kelliher:
"Does anyone have any ideas on what the problem could be?"

The CPES is dissolving(?) or drawing-out the residual oil (linseed or other) that was left in the timber. If it is oil ?, the varnish can be raised slightly or matt. It is amazing how poly (even as a varnish, which I presume is an oil/poly blend?) can help draw the old oil out (vrs sitting between the interfaces of each coat and causing problems later). It can be sanded off, and recoated, or more if needed. You have an eagle's eye Skipper, normally you will only notice this under coloured paints, especially the whites.

Warren.

[ 10-19-2004, 11:57 PM: Message edited by: Wild Wassa ]

[Scott Rosen]

If you started the work in the summer and just finished it 4 weeks ago, you may have waited too long to get the varnish over the CPES.

CPES has no UV protection. If your boat is exposed to sunlight, you will need to get 4 to 6 coats of varnish on right away. If you apply the CPES and then wait a couple of weeks, then apply varnish at the rate of one coat every week or so, you are asking for trouble.

[Scott Rosen]

Also, my experiences with Interlux varnish is that it goes on thin. I would put on at least eight coats, more if possible.

[Wild Wassa]

These kind of blotches? ... that I once had with poly over CPES.

Oil being drawn out of a (previously coated in varnish) foil.

http://www.imagestation.com/picture/sraid143/p620cd36c30789ed8ada6bf69ae21ffcc/f6919420.jpg

To the right of the yellow arrow there is a small patch of oil. This shows how irregular the problem can be. The problem can show up, about 3-5 minutes after coating or not until the following day.

http://www.imagestation.com/picture/sraid143/pae9f498b90c747055d08ea3577449cf3/f69193ae.jpg

Joins in timber can also exude oil, way after the event.

http://www.imagestation.com/picture/sraid143/pf05a7a2c55af5c2f21cae33081ea0cfa/f69177b5.jpg

Warren.

[ 10-20-2004, 05:05 PM: Message edited by: Wild Wassa ]

[paul oman]

What about the possiblity of amine blush from the CPES? That would impact topcoats of more epoxy or varnish.

Dampness of the teak during first treatment might also affect the CPES application in a negative way.

Just guesses on my part!

paul oman
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[Bob Cleek]

I'm not entirely sure what you mean by "oxidation splotches." If they are dark, it is probably moisture. Happens all the time. Particularly on toe rails, you can lay down a beautiful finish on TOP and still have bare spots or seams underneath the rail cap. Dampness will seek out anyplace that soaks it up and then it travels. This will cause the damper wood to darken under the finish. Often, it will lighten up again when the weather dries up. True oxidation (so called) in teak is merely weathering, coupled with some mold sometimes. To occur, the surface must be exposed to air and sunlight directly. It cannot happen underneath a coat of varnish, CPES'd or not. What you have is likely some moisture that has wicked up under the varnish. If it is occuring around a joint, it's likely that for sure.

[Wild Wassa]

These three photos are a better examples of what I thought your problem could be (if it is).

Again, not overlooking all other posts because there are quite a few causes of patchiness and mottle.

I cleaned the board and de-greased it (de-oiled it with solvent) prior to CPES'ing.

http://www.imagestation.com/picture/sraid144/pa069102d3eeb6baed46b44de20e7304d/f6838f83.jpg

The mottle and patchiness is evident in the centre of the board. The darker patches of rot make the board look salty, :rolleyes: .

http://www.imagestation.com/picture/sraid144/p3115f0bccaccf0a2ec01eb901b9f0747/f6838f3c.jpg

What I thought may have been the oxidation, is 'Callier effect'? The scattering and diffusion of light, internally reflected within the emulsion due to porosity (fine bubbles). I put four coats on this morning to exascerbate the problem. The raised areas are oil. The lighter areas are porosity.

http://www.imagestation.com/picture/sraid144/p1d302603769449115ca26fdd44d610d0/f6838ef1.jpg

Warren.

[ 10-25-2004, 06:42 AM: Message edited by: Wild Wassa ]