Conversion Varnish "Bubbling" Concern
Thinning, application and clean-up tips for trouble-free CV work. October 28, 2005
Question
I have been trying to apply SW water White CV with a Devilbiss Finishline 3 HVLP Gravity Gun, using a 1.5 needle with a #3 cap. Setting the pressure at 18 gives a pretty good finish but I am still getting a few bubbles, although it could be dried finish, as it’s there immediately after the spray pass. I am wondering if I should be using a smaller or bigger tip. So far the results are the best I have ever achieved. I am using gloss and could probably buff the bits out, but I would like them just not to be there. I filter going into the cup, but do not have a filter in the cup.
Forum Responses
(Finishing Forum)
From contributor A:
I tried SW CV after the local salesman offered a free 5 gallons. After several tries and calling in the factory SW tech, I decided it was not the finish for me. I had been using M.L. Campbell CV and was used to one coat sealer and one coat finish. SW CV had to be laid on thin to avoid bubbles and it was really bad on oak. The factory tech told me I would have to put on at least 2 - 3 thinner coats, that needed to dry in between and had to be sanded. This would have doubled or tripled my work, so I decided not to use SW CV. The salesman said he would look into a solution to my problem but after I told him that SW seemed to be an inferior product compared to M.L.C. he never came back.
From contributor B:
You might check for moisture in the air, as that can cause the bubbles as well. Try laying on a thinner coat. You can recoat without sanding if you recoat when the previous coat is still tacky. We never thin but you could try a little Xylene to help it flow a little better. The water in the air or having the freshly sprayed door in a moist air stream is the likely culprit. I remember you saying that you were in a damp climate.
From the original questioner:
Yes, it is definitely humid here. I have moved away from the CV as it is a real pain to clean your gun. There is nothing like a good lacquer base so lacquer thinner cuts it. There’s just something I don’t like about using Xylene to clean with.
From contributor C:
I have used lacquer thinner to clean my gun after spraying CV for a few years now. Once in a while a needle will push out any leftovers from inside your gun. As for the bubbles, the only bubbles I see are on that Chinese ply as the CV reacts to their glues.
From the original questioner:
When I ran lacquer thinner through my gun to clean it, it turned to gum.
From contributor B:
The CV is a bit harder to clean but is a much better product. We add a little acetone into the lacquer thinner to clean up. Once you get used to the CV you will not return to the regular lacquer. Don't give up so easily.
From contributor C:
All of that depends on how well and how soon you clean out your gun after spraying.
From contributor D:
R7K27 thinner mixed at 15% will probably solve your bubble problem. The K120 thinner with more elbow grease should solve the dirty gun problem.
