Why should we dilute our finishes before spraying?

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Forum topic by thedudeabides posted 11-17-2009 08:28 AM 7188 views 0 times favorited 14 replies Add to Favorites Watch
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75 posts in 3134 days

11-17-2009 08:28 AM

I understand the main reason to thin a finish is to reduce its viscosity and allow it to atomize properly in the sprayer, but with the proper needle I’m able to spray even heavy paints without dilution and without the problems normally associated with too-thick mixtures. So, other than to get it to work in the sprayer, is there any other reason to dilute your lacquers, paints, and stains?

14 replies so far

View Julian's profile


880 posts in 3519 days

#1 posted 11-17-2009 03:10 PM

One reason that comes to mind is that initial coats of finish need to soak into the wood a bit, and a thick coat won’t do that. Another reason to thin a bit is to alleviate any problem of brush strokes.

-- Julian, Park Forest, IL

View CharlieM1958's profile


16274 posts in 4212 days

#2 posted 11-17-2009 05:03 PM

I’m no spray expert, but it seems like running would be more of a problem if you were spraying on a thicker mixture.

-- Charlie M. "Woodworking - patience = firewood"

View woodsmithshop's profile


1318 posts in 3539 days

#3 posted 11-17-2009 05:37 PM

also cuts down on drying time, so you can spray on the next coat, and drying faster means less dust can settle in the finish.

-- Smitty!!!

View bruc101's profile


1200 posts in 3535 days

#4 posted 11-17-2009 06:41 PM

Exactly bentlyj.

-- Bruce Free Plans

View SST's profile


790 posts in 4188 days

#5 posted 11-17-2009 07:25 PM

The main reason to thin paint is to get it to go through the gun & be atomized in such a way as to lay down a smooth coat. Too thin & you don’t get enough pigment on the project or you get runs. Too thick & you get “gloppy” coats. Having spent a number of years in the auto painting industry, I learned that adjusting viscosity is really a “feeling” as much as a precise practice. I’ve gotten the best results by simply playing with the mix on some scrap for the best look & lay down. While spray guns will work in a relatively wide range of viscosity, there is a “best mix” for each product. Don’t be afraid to play with gun settings & dilutions. It’s cheaper & easier than buying additional fluid tips or drilling them out. One thing that reducing the mix also does is to effect drying time. Depending on what you use to reduce the finish (what type of solvent) you can retard or speed the set up time. this can affect runs. -SST

-- Accuracy is not in your power tool, it's in you

View BlankMan's profile


1490 posts in 3346 days

#6 posted 11-17-2009 09:37 PM

SST Thanks for the explanation, I kind of thought thinner would run easier. If you’re spraying something not really pigmented like poly what would indicate “too” thin?

-- -Curt, Milwaukee, WI

View BlankMan's profile


1490 posts in 3346 days

#7 posted 11-17-2009 11:51 PM

Yeah I know I have viscosity cups and use them but SST is suggesting playing around and that it’s part feeling so I was looking for some pointers on what to look for in lieu of the scientific approach.

-- -Curt, Milwaukee, WI

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790 posts in 4188 days

#8 posted 11-18-2009 05:57 AM

The cup is a good starting (and possibly ending) point. I don’t use one anymore, but only because I’ve kind of gotten the feel for how it looks when it’s right from just seeing it lots of times. I guess if you were to “play” a bit, you might want to start with the cup, & then try a mix that’s a little each side of (thinner/thicker) that ratio & look at ease of spraying, lay down (smoothness) & runability. (that’s probably not a real word) Also look at the cured result for clarity & hardness.
As to what I use to thin, Always check w/ the manufacturer for their suggestions first. Some things I have used (keep in mind that I’m not necessarily recommending them) include turpentine, mineral spirits, naphtha and lacquer thinner. Lacquer thinner is useful in that it evaporates quickly so the finish lays out really nice, but because it evaporates quickly you don’t get runs, but, BUT, BUT…Never, never, never (am I making myself clear on this point) use this without adequate ventilation, (I’d suggest only use it outdoors to be safe) and test it to see how it reacts with the finish you’re using. There probably will be a lot of guys who’ll say don’t use it, and maybe that’s good advise. Whatever you do, don’t try anything you’re not comfortable with.

-- Accuracy is not in your power tool, it's in you

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Chris Wright

540 posts in 3474 days

#9 posted 11-18-2009 06:23 AM

In my experience with spraying, I only need to thin lacquer down if I’m spraying from by suction feed gun. If I’m using a gravity feed gun or a pressure pot then you shouldn’t need to thin your lacquer. As for paint, I don’t have much experience spraying much other then some latex and I’ll usually add a little water to get it to flow a little easier.

-- "At its best, life is completely unpredictable." - Christopher Walken

View thedudeabides's profile


75 posts in 3134 days

#10 posted 11-18-2009 02:33 PM

The reason I asked is that I’ve got my cabinetry painted white and sanded down to 600 grit. It’s now ready to accept the lacquer coats. I’ve got Minwax Clear Brushing Lacquer that I plan on spraying with my HVLP system. It’s cold and dry here in New England and I’m having a hard time trying to decide how to proceed with the lacquer spraying. I’m assuming the Minwax is good old-fashioned nitrocellulose and will ventilate accordingly.

I’ve seen recommendations from no thinning all the way down to 50/50 mix. I’m going to try a few test samples and the spray the back doors of the cabinets first, but I’m pretty much committed to the Minwax, since it’s all you can buy around here.

Is this something you would attempt to spray 100% lacquer first, and thin for the final coat?

View rhett's profile


742 posts in 3661 days

#11 posted 11-18-2009 03:13 PM

I have had good luck spraying laquer when its cold by warming up the laquer prior to spraying. Put the can in a bowl of hot water with the lid cracked. Thinned or not, cold weather makes for thick finishes. Just use caution not to get water in the laquer.

-- Doubt kills more dreams than failure.

View Kent Shepherd's profile

Kent Shepherd

2718 posts in 3280 days

#12 posted 11-18-2009 08:49 PM

Usually, if the lacquer is too thick when you spray it you will get orange peel, although it does depend a lot on the equipment you’re using. When I use my airless sprayer, I don’t thin as much as when I use my conventional spray equipment. To further complicate, I thin more for my suction gun than for my pressure pots. Again, so many questions here are difficult to answer bacause there are so many variables. I hope this helps instead of confusing the issue.

Good luck with your project.


View KB1's profile


28 posts in 3146 days

#13 posted 11-19-2009 08:32 AM

My HVLP system is not so versitile that i can spray latex paints without thinning. One of the first replies in this thread mentions drying time. I will typically dilute latex by 35-50% for my gun. Be sure to add some Floetrol with the water. Shoot it twice, comes out real nice. Dries real quick. Now when it comes to clear finishes I am surprised that any of you professionals are still using NC lacquer. I live in Fl the humidity state. It is used only ocassionally when tinted black. For clear coats I am now using Crystalac super Premium, H20 based. Available from Mc Feeleys catalogue. This stuff is the best, dries fast. You can apply 6 coats in a day. No fogging, great flow out, very few fish eyes, just don’t spray it on too thick. My 2 cents worth. KB1KNOB

-- KB1KnoB

View thedudeabides's profile


75 posts in 3134 days

#14 posted 11-20-2009 05:00 PM

So, I’ve been spraying lacquer non-stop for the past two days. From what I’m seeing it’s more important to get the level of spray adjusted properly on the HVLP sprayer than the dilution. I’m diluting about 20% with lacquer thinner, and with the right amount of atomization the results are very promising. No orange peeling, fish eyes, or runs, and a nice mirror finish. I’ve got six coats, and plan on hitting it with another three today after some wet sanding with 500 grit. Thanks for all the advice so far, I couldn’t have done it otherwise!

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