water based poly causing warpage

[scott vroom]

I'm continually battling warpage that occurs after spraying water base poly paint on (primarily larger) drawer fronts. See the pic below...it's a 12-1/2" tall x 32" wide drawer front. Soft maple, 11/16" thick, and is warping cross-grain. I've found that if I flip the board over and spray a thick coat on the back side it usually pulls the drawer toward flat. Anyone else dealing with this? Any tricks that might minimize the effect? Perhaps first coating with an oil sealer such as Arm-R-Seal would help by not allowing the water based poly to penetrate the grain?

This particular drawer front will be attached to a tall drawer box (10 1/2") so 2 mounting screws centered will likely pull it flat(er).

[Myk Rian]

Give it time. You made one side wet, it warped. Let it dry. It'll go back to flat.

[scott vroom]

Give it time. You made one side wet, it warped. Let it dry. It'll go back to flat.

Myk, it's cupped after 4 hours of curing in a 75 degree shop....I don't think it's going to flatten on it's own, it never has in the past. The only solution I've found is to apply a coat to the opposite side, it often pulls it back toward flat. I'm looking for a solution to avoid the problem altogether.

I tend to lay on the primer undercoat very thick as it acts as a filler and sands extremely well (GF White Undercoat poly). Maybe I'll try applying several light coats, building up the primer slowly. I was just hoping to find others that have dealt with the situation and could offer tips.

This particular 10-1/2" tall board was glued up from 2 smaller pieces; I think I might have been better off gluing up 3 or 4 smaller boards, alternating the grain direction.

Right now I feel like a hack and want to learn my way out of it.

[John R Allen]

I reccomend using BIN primer.

[Chris Padilla]

Alternating grain won't help. You need to seal both sides (shellac, for example) or simply apply the finish to both sides to equalize things as you've found out.

[Max Neu]

Just spray both sides at the same time.I spray the back, flip it over, then spray the edges and face.I do this on trivets with sharp screws, leaves tiny marks that you can barley see.You don't have to do it this way on your topcoat if you are concerned about the marks on the back, but you can at least get it sealed without warping.

[peter gagliardi]

Two words- solvent based. I won't use a water base finish for this reason, and a few others!
I spend a fair amount of time and energy maintaining optimum humidity control in my shop, I don't want to introduce extra moisture that can involve predictable, and sometimes unpredictable movement.
A water based finish will raised the moisture content of a piece of wood by several percent or more depending on thickness, species, etc...

[Max Neu]

I agree, I only use solvents ( 2k poly), but not everyone has the facilities to spray solvents. That being said,if you spray both sides at the same time, it should take care of the problem. Kind of like putting glue on one side of a piece of veneer, it will curl up like a potato chip, but if you mist the other side, problem goes away.

[Joe Calhoon]

Hang them and spray everything at once. We have been using WB on exterior work for a few years and that is the best way to do it. Most of the WB finishes are made to have good vertical hold for this reason.

Joe

[Mark Bolton]

+1 to spaying both sides at once. We are 100% water based and woudnt go to solvent unless I had no other choice.

[scott vroom]

Hang them and spray everything at once. We have been using WB on exterior work for a few years and that is the best way to do it. Most of the WB finishes are made to have good vertical hold for this reason.

Joe

That was my first thought...but these are drawer fronts with visible edges...how do I spray everything at once without drilling suspension hole(s)? For cab doors, I use the Rockler hangers that lock into the 35MM cup hole which allows 360 degree spraying...no problem.

I'm going to try Chris' suggestion to seal first with (non-waxed) shellac on the next phase of the current project.

[Peter Quinn]

Probably better off with two light coats of primer, sand and level between. With a thick coat the finish skins, traps more moisture and solvent, takes a wile to work out, tries to escape through the back rather than evaporate. Running some air movement equipment in the drying area may help too, decreases time for water to flash off. Just finished a job where we sprayed about 35 gallons of WB poly, no issues with warping on mostly plain sawn WO, did seal both sides in sequence, but rather close together. Seal backs, seal fronts, sand repeat, sand, full top coat, buff. You run the risk of incompatibility with a solvent sealer and subsequent WB top coats unless the sealer is completely dry and all solvent is flashed off. I've sealed with shellac to avoid grain raise under WB pigmented, seems to work well and dries quickly.

[Bradley Gray]

I do a light coat on the back then flip onto a sharp edge and light coat the edges and front.. Once everything is sealed the warping isn't an issue.

[Mark Bolton]

its an applied front no? why cant you spray the back, flip onto stilts as Max said, and spray the front? First coat only so if you get some nib marks on the back (which wont be seen anyway) you will scuff them out and cover them on second coat (which can be done one side at a time).

[Peter Quinn]

its an applied front no? why cant you spray the back, flip onto stilts as Max said, and spray the front? First coat only so if you get some nib marks on the back (which wont be seen anyway) you will scuff them out and cover them on second coat (which can be done one side at a time).

Issue is now its wet on all 6 sides...and its in the booth, how to move it to drying area. We ran assembly screws into the blind area on the backs where the drawer box covers, shoot the backs, flip, shoot the edges, shoot the face, walk it away holding the assembly screws. You have to have a lot of horizontal drying space, racks don't do well this way. I suppose you could even drill a shallow false 35mm pocket to use the door hangers too, again into the blind spot.