Joint Telegraphing Problem with Conversion Varnish

      Trying to identify causes and solutions for lines that show up at wood joints late in the finishing process. February 29, 2012

Question
I am preparing to finish a set of cabinets with a tinted conversion varnish. They will be an off white color. The cabinets will be made with maple veneer goods and the face frames made of German beech. The doors will be flat panel shaker style with German beech frames and MDF panels. I have done some work with this type of finish some years ago using MLC Clawlock for a primer and resistant for a top coat that was tinted, and had no issues.

This go, I am trying one of two different finishing schedules:

1. MLC Clawlock, and their new Stealth topcoat tinted

2. Gemini Conversion Varnish both as a sealer and top coat - not the premium CV as it is not available in a white base to start.

Also both of these are a semi gloss/satin sheen finishes, prepared just as the manufacture requires, and all coats were shot at 4-4.5 mils thick as prescribed. I have already prepared some samples of these on both plywood and hardwood. The Gemini product worked well but with its lower solids content it tends to show any imperfections/irregularities. I have spent a lot of time on the sanding schedule and have worked hard to remove and or fill anything as needed. Thus it will most likely require an additional coat of primer and another sanding step!

The MLC route worked really well in filling in these minute imperfections building up quicker and performed as well as I remembered them to. The only problem I am having with both of these is that after the finish has dried you can see a fine line where the rail and stile meet. This was sanded completely level/smooth to the touch! I'm not quite sure what is going on here.

Could it be that the glue line is swelling just a little when it comes in contact with the finish? I did prepare both of the face frame samples, sand and then finish within an hour or so of building them. Would this be mitigated if it had a longer time to cure/dry out, say overnight? Or is this something that others have experienced when working with this type of finish? The line is small but noticeable with light at the right angle. Any help or advice would be greatly appreciated.

Forum Responses
(Finishing Forum)
From contributor G:
We used the same products (stealth with white vinyl primer), the same style doors and achieved the same results. We prepared the doors a day or two ahead of time and didn't have a problem until the primer was applied. We just puttied the joint after the primer and they disappeared. Definitely a paint and I'm not sure why this happens or what can prevent it.



From the original questioner:
I should say that a better description would have been a Pigmented CV. I am curious about what you mentioned. The joint is completely filled and very even from rail to stile with either a tight jointing of the two hardwood pieces and/or a little famowood filler as needed. The joint sands smooth before the primer is applied and after the primer is sanded and I don't see the line until after the Stealth/Gemini CV is applied as a finish coat. Iím not sure why this is?


From contributor G:
I cannot remember if the crack at the joint is there after primer or after the first coat of stealth. Now that I think about it it is after the first coat of stealth (because Iíve worried about the putty not taking the finish as well as the rest of the door that already has a coat of primer and one coat of stealth). I don't have any idea why this happens. Luckily we don't do too many jobs like this.


From the original questioner:
So you say that the crack may show up after first coat of stealth, are you applying more than one coat of stealth, and if so does it get any better? I had planned on only one 4-5 wet mil thick coatings of both the Clawlock primer and the stealth top coat. I understand that if desired I can also apply a coat of Krystal atop all this for even more durability but would prefer not to add this step unless absolutely needed.


From contributor G:
I'm using an AAA pump so Iím typically spraying 3-5 mils per coat and spray one primer and two top coats. I usually get good coverage with the first coat of stealth and add a second coat for additional protection (and just in case things don't turn out perfect with the first coat).


From contributor L:
Glue up the doors and sand them with a heavier grit sandpaper. Do something else for a day or two. Then sand with your final grit. Use Clawlock thinned at 10%, spray 4-5 mils. Sand again hard using 220. The primer should be semi-transparent at this point. Spray another coat of Clawlock thinned at 10%. Let dry, sand lightly with 320 and spray your desired finish.


From contributor R:
One thing I've noticed when finishing pieces done with multiple types of materials is if I put on two-three coats of sealer and smooth them well, the primer, or undercoats and topcoats go on much more evenly. Itís hard to tell where one material stops and the next starts.



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