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Finishing AC Plywood

Gary Member

I work for a company that finishes a lot of AC Ply. I am doing a job right now using S.W. Kem Aqua Plus with just a touch of Black pigment. When I spray it out this is what I get. See attached photo. Any help in figuring out what causes this seperation.

View higher quality, full size image (3264 X 2448)

6/22/16       #2: Finishing AC Plywood ...
rich c.

I'm guessing cracks in the thick veneer face and surface tension of your finish. You might have to rub on a base coat of stain.

6/23/16       #3: Finishing AC Plywood ...

I agree with Rich,I just started using Kem Aqua plus about 50 gallons ago and I discovered it needs a pretty fine, even scratch and dusting between coats to break down the surface tension. A 3M fine sponge has been working for me... I'm guessing that a quick pass with a RO and 400 grit would work too.

6/23/16       #4: Finishing AC Plywood ...
Gary Member

I tried rubbing in a stain prior to finishing, did not work, also sanding in between coats with 320 grit on a corian block sander.

6/23/16       #5: Finishing AC Plywood ...
rich c.

Sorry for that double post. I'd suggest a better grade of plywood if that finish is unacceptable. Can't say I've ever seen anyone look for a nice finish on AC plywood.

6/24/16       #6: Finishing AC Plywood ...

I've you give a try with a pre conditioner of sort ( diluted sanding sealer)
Oak is notorious for similar troubles !!

6/24/16       #7: Finishing AC Plywood ...
Arthur Grudko

The glue used to laminate the plywood likely has formaldehyde which is evaporating. It is not compatible with a waterborne coating.

6/24/16       #8: Finishing AC Plywood ...
D Brown

It may be the glue calendaring through the face veneer .

6/25/16       #9: Finishing AC Plywood ...
Paul Snyder  Member



Make sure the plywood is completely sealed before spraying the toner.

6/25/16       #10: Finishing AC Plywood ...
D Brown

Usually even if you seal over glue it will not take color well in my experience.

6/27/16       #11: Finishing AC Plywood ...
Gary Member

The color is in the top coat, I made a shader for the color. This particular color requires 2 coats sprayed out at 5 wet mils, the first coat being used as a sealer, with a 320 scuff in between. I have to think that it is surface tension,and or something in the substrate, starting to break down or off gas. I have used a grian filler and that does take care of the proplem, but it also know adds 2 extra steps to the finish process. On a side note, I have 33 kitchens to do using a rift sawn white oak veneer, using the same type of shader, but this time white. I did not or do not want to add the extra steps, That's why I was hoping some one has run into this problem, and came up with a quick fix.

Thanks for the replies

6/27/16       #12: Finishing AC Plywood ...
Paul Snyder  Member



It can take multiple coats of WB finish to seal the wood completely - depending on the type of wood. If it isn't sealed 100%, every pin hole in the finish leaves a divot in the color when you spray the toner. In the case of the plywood you're using, the holes are lines along the grain of the wood. Switch to a solvent finish and you won't have the same problem.

6/28/16       #13: Finishing AC Plywood ...
Gary Member

Unfortunately I can't switch, we are going green and getting out of the solvent base finishes

6/28/16       #14: Finishing AC Plywood ...
JoeW Member

I only use Waterborne products. I have had this issue every time I have added color to a clear waterborne Lacquer. It has helped to seal the wood with several coats of clear first. But it has never been a great finish. I do believe it's a tension issue.

The reps from both Valspar and M.L.C. have told me it's an issue they are still working on.

6/28/16       #15: Finishing AC Plywood ...
Gary Member

yes I run into this a lot also, but unfortunately adding the extra seal coats, adds extra cost to the finishing, and that I have no control over,

6/28/16       #16: Finishing AC Plywood ...
Paul Snyder  Member


Gary - spray the toner coat(s) much lighter - just barely wet - about 2 mils. This will help reduce the crawling effect you see. It helps to thin the finish with water about 15%.

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