Cross-Brand Use of Lacquer Thinners

Thinners are formulated to work with certain coatings (and vice versa). But using a different thinner brand can serve certain purposes if you're careful. October 28, 2005

Question
Can any lacquer thinner be used to thin, or do you need to use a specific brand? What I'm wondering is, would I be able to use Sherwin Williams or maybe just more of their flow extenders?

Forum Responses
(Finishing Forum)
From contributor R:
I would suggest using MLC's brand of thinner or use their Flow Enhancer #2 during the warm summer months.



From contributor L:
I use MagnaMax Dull all the time. I don't thin it at all. I use a gravity feed top cup HVLP gun, and not a good one either. I shoot with the input pressure at 43 PSI using a 1.7mm tip. I get an 8" fan with a 5" center. This works pretty good for most of my needs. When I have to do some larger stuff I wish I had a larger fan pattern, but I can do well with what I've got. I used to use hardware store lacquer thinner to thin it down to 25 sec (Ford #4 cup) and never had any problems.

I think you can use up what you have in stock without too many worries. After it is gone, switch to the MLC brand and you will have good reliable results. When you spray, don't be discouraged by how it looks shortly after you lay it down (orange peel). It will look better the next day after it has stretched itself out and flattened down. It took me a while to get used to this aspect of MagnaMax.



From contributor D:
The MLC lacquer thinner is formulated to be used with their coatings. Put another way, their coatings are formulated to tolerate the MLC lacquer thinner best.

One risk in using a different lacquer thinner is creating a recoat window. This risk seems to be low because it has not happened to me and I use different lacquer thinners often. Woe to me when it does happen and that's the breaks for being a maverick and not following the spec sheets to the letter.

I prefer Sherwin-Williams lacquer thinner to the MLC thinner. I also prefer the Dupont thinner that you get in an auto body supply store to the MLC thinner. I like the other thinners because they make better cleanup thinners. They are hotter (they supposedly have more solvency). The MLC thinners are formulated to be weak when compared to other lacquer thinners. This is done so that the MLC coatings do not develop that recoat window.

This can happen as a new coat tries to interfere with a curing/cross linking undercoat. The new coat wants to bite in chemically and the curing undercoat wants to resist because it is getting its tough film. What happens in this tug of war is wrinkling and that is the recoat window being hit.
So far I have had no problem adding acetone to my mix of Duravar or Magnamax. It may inhibit some of the flow-out, but on the first coats I do not care since these will be sanded anyway. I need those first coats to dry quickly so that I can flip the drawers/doors without the surfaces sticking to the rack. Acetone also helps.

Acetone also quickly lowers the viscosity of the coating. You can use less reducer if it is sopped up with acetone because it does lower the viscosity much better than a regular mix of lacquer thinner (because of the greater solvency of the acetone).

Acetone also helps with that chemical bite into the undercoat, whether it is vinyl sealer, Clawlock, or the topcoat coating itself. That same eagerness to bite into the finish is what can also trigger the recoat window. Use a different thinner at your own risk. Now you know the issues. You decide for yourself how thin the ice is that you want to walk on.



From contributor B:
Contributor D is absolutely correct in the statement that acetone can facilitate a recoat window, so use with caution. Wrinkling is usually the result. I have been told that normally 2% is considered the max. Using acetone in high humidity weather can also lead to blushing.

Remember lacquer thinner is a blend of solvents that are a compliment to the solvent package contained in the product being sprayed - experiment with caution.