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.

[Mark Bolton]

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.

We have nails driven through ply scraps. You move it to the drying rack with the ply. No need to touch the part. You need them anyway to flip if you wet your edges spraying the back

[Max Neu]

We have nails driven through ply scraps. You move it to the drying rack with the ply. No need to touch the part. You need them anyway to flip if you wet your edges spraying the back
That's how I do it, I have pegs coming out of the wall in the drying room for long pcs. And mobile racks for things like cabinet doors and drawer fronts, the doors and trivets get racked together.My racks are made with extra room to allow for the trivets.

[thomas hsieh]

Its too bad. I would Leave it alone. Eventually it will flat out.

[Peter Quinn]

We have nails driven through ply scraps. You move it to the drying rack with the ply. No need to touch the part. You need them anyway to flip if you wet your edges spraying the back

I see that working better with some assemblies than others. Our finisher does that as well, but sometimes it's like that old game operation trying to get the parts on he drying racks w/o touching the rack above, and the rack has a slight back angle which gives heavy drawer fronts an opportunity to slide across the finish nails. Last place had adjustable wall racks w dowels in the drying room, bit more flexible. Seems any system can be made to work. Don't think the present rack is adjustable?

[scott vroom]

I'm picking up some great ideas from this thread...thanks guys. I'm surprised there aren't many suggestions to seal the wood with a moisture resistant finish. It stands to reason that if WB moisture is the culprit then an oil or shellac sealer would reduce/minimize this effect. I guess I'll do some experimenting, beginning with Chris' suggestion re: shellac (dewaxed I assume).

[Mark Bolton]

I see that working better with some assemblies than others. Our finisher does that as well, but sometimes it's like that old game operation trying to get the parts on he drying racks w/o touching the rack above, and the rack has a slight back angle which gives heavy drawer fronts an opportunity to slide across the finish nails. Last place had adjustable wall racks w dowels in the drying room, bit more flexible. Seems any system can be made to work. Don't think the present rack is adjustable?

Dunno, no problems here. Worst part is dealing with the stilts/storage but I don't use them for everything. No issues with the racks again other than loosing some rack volume to the stilt thickness.

I'm not a fan of spraying hanging parts or hanging them to dry I've had too many occasions where they swing/twist and bump each other.

But I'm not a dedicated finisher and I don't finish every day either.

[Jason Beam]

I'm picking up some great ideas from this thread...thanks guys. I'm surprised there aren't many suggestions to seal the wood with a moisture resistant finish. It stands to reason that if WB moisture is the culprit then an oil or shellac sealer would reduce/minimize this effect. I guess I'll do some experimenting, beginning with Chris' suggestion re: shellac (dewaxed I assume).


Doing so is symptom treatment. It's not the water that's the problem. It's the uneven application of it that's causing the warpage. You'll no doubt have some results by sealing first - but now you've added a step to your process rather than solved the root problem: water applied to the surfaces unevenly. The suggestions to finish all sides at once are solving the cause by changing the process without adding steps or materials or drying times.

[Mark Bolton]

I'm picking up some great ideas from this thread...thanks guys. I'm surprised there aren't many suggestions to seal the wood with a moisture resistant finish. It stands to reason that if WB moisture is the culprit then an oil or shellac sealer would reduce/minimize this effect. I guess I'll do some experimenting, beginning with Chris' suggestion re: shellac (dewaxed I assume).

The stinky part about that option is its an additional (unfunded) step in an process that's already time consuming and costly.

I just always look to a way to solve the problem without adding steps or even eliminating a few. If you can first coat the entire part in one drying cycle you've eliminated the second drying cycle and its associated handling.

It basically takes a drawer front from 4-6 (six if yiu have to run an additional sealer) coats down to three. That's a massive time and cost savings.

[scott vroom]

The stinky part about that option is its an additional (unfunded) step in an process that's already time consuming and costly.

I just always look to a way to solve the problem without adding steps or even eliminating a few. If you can first coat the entire part in one drying cycle you've eliminated the second drying cycle and its associated handling.

It basically takes a drawer front from 4-6 (six if you have to run an additional sealer) coats down to three. That's a massive time and cost savings.

I don't disagree with anything you said, but I'll add that re-milling cupped drawer fronts is even more costly both in time and materials. Shellac dries quickly.

Going forward I'll be taking the advice of coating both sides in a single drying cycle using the method described (plywood base with screws positioned so that their mark falls on the portion of the drawer front that will be hidden when attached to the box).

Thanks a lot folks, very helpful discussion for me :)

[Max Neu]

Scott,
When you make the trivets, don't feel like you have to size them and position the screws just for that particular job.Most of mine are 6" × 24" with a set of 4 screws towards one end, and another set of 4 screws at the other end.That way they will work for small pieces, or longer pcs.Even though they have 8 screws, only 3-4 will make contact on the bigger pcs.Making them more universal will eliminate the need to make new one's every time.

[Myk Rian]

Its too bad. I would Leave it alone. Eventually it will flat out.
That's what I suggested, because that's what worked for me. But apparently it's a rush job with no time for waiting.

[scott vroom]

That's what I suggested, because that's what worked for me. But apparently it's a rush job with no time for waiting.

It's been 2 days and the panel has not self corrected. Myk, how long did it take for your piece to flatten?

[Myk Rian]

Several days. It was a rosewood box I made for my Aunt using wood my late Uncle had. It was a 1/4" top. It warped when I finished it, so I made a new one. Got that finished and delivered to her in Florida, and the original one straightened out. Ticked me off because the original was nicer grain.

[Mark Bolton]

I'm sure many factors apply but I've had this happen on 4/4 material and they never came all the way back. But for a drawer front generally the concave is on the back because that's usually your first coat and if it comes back almost to flat often fastening it to the drawer box will pull it to flat.

[Max Neu]

Maybe clamping it flat against a couple of straight edges for a few day's (if you have the time to wait)might take some of it out.I know alot of times it doesn't work,but you never know,it might help some.

[Joe Calhoon]

From our early WB experience they usually come back. To me it is just easier to figure a way to coat both sides and be done with it without trying to seal with another material. There are several good ideas here on how to do it.
Joe

[thomas hsieh]

How big is the gap? Is it thickness of a paper?

[Chris Padilla]

Pick up a can of SealCoat from one of the borgs, Scott. It is a 1 or 2# cut of dewaxed shellac made by Zinsser. Yes, it does dry very quickly so you can spray both sides within 20 minutes of each other on average. Then you can apply your WB finish and likely take your time before coating the back and you should solve the warping issue. As many folks noted, there are a few ways to address this. I like the idea of coating both sides right away...no reason to add steps if you don't need to.

[scott vroom]

Pick up a can of SealCoat from one of the borgs, Scott. It is a 1 or 2# cut of dewaxed shellac made by Zinsser. Yes, it does dry very quickly so you can spray both sides within 20 minutes of each other on average. Then you can apply your WB finish and likely take your time before coating the back and you should solve the warping issue. As many folks noted, there are a few ways to address this. I like the idea of coating both sides right away...no reason to add steps if you don't need to.

Yeah, I'm going to give the shellac a try...

Chris, I'm in Mt. View...where are you located?

[John R Allen]

BIN primer is shellac based and gives you the white undercoat. I think it sands better than the GF undercoat too and doesn't raise the grain. It seems like that would take care of both the sealing and priming without adding any steps.

[Phil Thien]

If these are applied drawer fronts, couldn't you just screw hook eyes into the back and hang them to be finished?

I've used the screws/finish nails through scraps but I'd still rather hang anything I've got to finish.