We are using water based stains and water based UV top coat for our finishes. It has been determined that the sugar in the maple is occasionally crystalizing from the heat of our ovens and is showing up under the finish as white specks. Has anyone else ever had this problem?

Dan, I have seen and heard of this happening on other jobs. It has nothing to do with your coating or ovens.
Your lumber was not properly kiln dried to convert the sugars. Go back to you lumber supplier and see what he will do.....
Good Luck!

Bob, thanks for the response. The strange thing is the white specks are only on the face of our doors and not on the back side. It is never in the veneer and only occasionally in the face frames. Mostly doors and drawer fronts. By converting the sugars does the kiln need more heat or time? Any idea what is not happening?

The one time I saw this happen it was only on fronts of doors.
If I remember correctly the kiln needed to be a higher temp to convert the sugars.

Do you guys run a puck to check your millijoules? Could you possibly bump up your line speed to hit your minimum cure spec and do some adhesion testing? This could eliminate a margin of surface heat if you can get it out of the lights a tad faster...

I would like to know if the same would happen if we use solvent base stain and regular uv coating?
Maybe the water on the actual system is helping the sugar appears anyway?

We do run a puck to check the UV power. I don't really want to bump the line speed as it will make the pace too fast for the seal sanding done on line. We have had this sporadic problem for 2 year's. It started to show up when we switched to water UV from a solvent UV finish.

Being waterbased does promote the issue and it tends to show up in the coating or bleeds to the surface.
Solvent base will not have these issues.
I did some searching in notes and the kiln needs to be at least 150 deg F or higher to convert the sugars in the maple.
I bet the reason your problem "comes and goes" is due to the inconsistent lumber drying temps.
Being UV has nothing to do with it. It is because the coating started off as a water based coating that redissolved the soluble maple sugars

Reading further into notes I have, reaching 150 deg F or higher during drying will change the composition(or converting) of the maple so the sugars will not bleed, thus not technically "converting" the sugars themselfs. Sorry for any confusion.

Thanks Bob, I will be contacting our lumber vendors.

Hello Dan !
I was wondering what would happens if you return to use the solvent stain , I believe the water stain is causing you problem.
Good luck

We were using water based stains for 2 years before we started using water based top coat and had no issue. It started when we switched to water based top coat. All of our lumber vendors are drying their lumber to well above 150 degrees and have not heard of this issue before.

Dan, to find out what is going on we need to know more about your process. You say it has never shown up on the backs of the doors? What is being done different on the fronts than the backs?