Understanding Lacquer Thinner

Is it okay to combine your preferred brand of finish with a thinner made by a different manufacturer? Here's a close, careful look at that question. April 29, 2013

My supplier has continued to increase price on M.L. Campbell lacquer thinner till it’s now over $31.50 per gallon. Does anyone know if Sherwin Williams or another brand will be okay to thin M.L. Campbell finishes with, especially Resistant and Clawlock?

Forum Responses
(Finishing Forum)
From contributor F:
I understand your frustration but that road will take you further than you want to go. Sooner or later it will lead to disaster. We have experienced brand X thinner being added into MagnaMax opaque and the set of cabinets streaking yellow. SW and MLC take a totally different approach to solvent development. For instance SW uses a lot of MEK and MAK to where MLC only uses Keytones limitedly. All thinner is not created equal. Plus if you ever had coating failure you will be left eating that cost because you used multiple manufactures. I know that this is not what you want to hear but I would rather help than hinder. I would thin Clawlock but I don't recommend thinning Resistant unless absolutely necessary. Hope this helps.

From contributor D:
Is that for the standard thinner? If so that's pretty steep. I keep thinking of going to fives to save a couple bucks, but it’s a hassle to handle. I don't know where you’re located but unless you’re outside of the lower 48 I'd talk to someone at your supplier and ask why they're so much more expensive than everyone else. I have used the hardware store items on a couple "emergencies" when my supplier was closed with no ill effects. For the few extra bucks I like the peace of mind of staying within the same brand.

From contributor A:
The prices for these solvents will continue to rise. The chemicals in that can are a bargain if you think about it. I order 55 gallon drums of lacquer thinner at a time (we use Becker Acroma and some Campbell products) but we keep reducers for both. It's best to not mix and match when the professional chemists have done all that work for you.

From contributor C:
I personally have never had much problem when mixing and matching. I always spray full strength and use retarder on a blush. I cut Clawlock recently with Home Depot thinner in an emergency one cup to a gallon. It flowed like glass. I top coated it and shipped it 12 hours later. It was beautiful.

From contributor J:
I use Valspar, but assume MLC would be comparable. If you like working out of one gallon pails or however it comes at that quantity, just pour it off from the five into the smaller container (you must have some empties).

From contributor F:
Lacquer thinners have different ingredients in their recipes that work well with corresponding ingredients in their top coat products. That doesn't mean using a different brand of LT will cause problems, just that it may not be as well suited, and as some have mentioned it could react unfavorably.

From contributor E:
Different finishes within the same brand are very different and may use completely different types of solvents. So just because one brand may own another does not mean their finishes are the same or that the solvents used to reduce them are interchangeable.

Finish chemists go to great lengths to develop solvent packages to work optimally in different finishes and unwittingly swapping them out for something different is just asking for trouble. It helps some if you learn the difference between generic terms like lacquer thinner and retarder and the specific chemical names of individual solvents like Butyl Acetate, Acetone, and etc. But for most of us the best bet is to bite the bullet on cost and use the solvent that the manufacturer says to use.

From Paul Snyder, forum technical advisor:
Lacquer thinner isn’t as mysterious as it seems. It’s a blend of solvents from the following solvent “families”:

Ketones - acetone, Methyl Ethyl Ketone (MEK), Methyl n-Propyl Ketone, Methyl Isobutyl Ketone (MIBK), Methyl Isoamyl Ketone (MIAK), Methyl n-Amyl Ketone (MAK), Diisobutyl Ketone, etc.

Esters - Ethyl Acetate, Isopropyl Acetate, Propyl Acetate, Isobutyl Acetate, Butyl Acetate, Methyl Amyl Acetate, Propylene Glycol Methyl Ether Acetate (Eastman PM Acetate), Amyl Acetate, Ethyl 3-ethoxypropionate (EEP), etc.

Glycol Ethers - Propylene glycol monomethyl ether, Propylene Glycol Butyl Ether, Ethylene Glycol Butyl Ether (Butyl Cellosolve, Eastman EB), etc.

Alcohols - Methanol, Ethanol, Propanol, Butanol, Diacetone Alcohol, etc.

Petroleum Distillates - Toluene, xylene, “high-flash” naphtha (fast evaporating), naptha, etc.

The solvents in each family are listed according to how fast they evaporate, fastest to slowest. In these blends, the Ketones, Esters, and Glycol ethers have the strength to actually dissolve the lacquer and are called “active” solvents. Alcohols don’t have the strength to dissolve lacquer, but work in combination with the solvents that do, so they’re called “latent” solvents. Petroleum distillates don’t have enough strength to dissolve lacquer but are useful to adjust viscosity (how thick/syrupy or thin/runny the finish is) and they’re called “diluents.”

If the lacquer thinner contains too much alcohol or diluents (which is sometimes the case with inexpensive brands meant for parts cleaning, not coatings), the lacquer will not stay dissolved and will come out of solution causing it to turn white or have white chunks in the final finish. Also, mixing too much oil-base stain with your finish to make a toner will cause the lacquer to come out of solution (oil-base means petroleum distillates). That’s why it’s a good idea to thin the stain with lacquer thinner or one of the ketones before mixing it with the lacquer - it makes it compatible by lowering the percentage of petroleum distillates.

Good brands of lacquer thinner that are made for coatings are interchangeable. I buy a good quality, no-brand name lacquer thinner in 55 gallon drums and the price is very good compared to buying it in smaller quantities. The main differences between brands will be minor variations in the evaporation rate and the HAPs and VOCs.

Slow evaporating active solvents (e.g., MAK, IBIB, Butyl Cellosolve, etc.) are called retarders. You can add these in small quantities to eliminate blushing. Also, if your lacquer has orange peel or dry spray, thin it with more lacquer thinner and adjust it slightly with medium to slow evaporating solvents to improve its flow-out. Personally, I always have a supply of MAK on hand because it's also compatible with 2K poly.

By learning about the solvents in the finishes you use, you will have the ability to get better results in a wide range of situations. Then you’ll need to find a supplier that stocks the solvents you want.

From contributor D:
CM, flow enhancer, retarder, and lacquer thinner all perform the same function - to thin the lacquer and allow it to flow out. You use different combinations depending on the weather. I keep a little cheat sheet my supplier gave me to know when I need to add a little reducer or retarder to the mix.

So for most of the winter I go straight lacquer thinner. Once we start into the summer months I start subbing a little reducer, as straight LC evaporates too fast. Then if it's really hot and humid I'll break out the retarder.

Lastly all finishes are different viscosities, if you have one you can spray right from the can that's great. Most that I've used do require some degree of thinning to be able to spray them out. Depending on the equipment some may need a lot of thinning. For instance a Turbine HVLP requires significantly more thinning than a AAA setup. The minimum for me is 10% and some finishes go up to 20% also depending on the conditions.