Viscoscity cups? HELP PLEASE

[Joe Jensen]

I've lost my touch with spraying NC lacquer. It keeps coming out too rough. Not fish eyes, just not flowing right. I did a fair amount of spraying years ago and developed pretty good technique and results with Mohawk NC. I no longer use enough to buy in the quantities they want to sell. I haven't been able to get the results I like with shellac, or any of the lacquers at the big box stores. Does the lacquer matter a ton? How about the Behlens NC from Woodcraft. I understand that Behlens in the retail version of Mohawk, just a more limited selection.

I tried shellac on the 8 jewelry boxes I'm building, and other than getting several coats on to build, the finish is terrible. I am having to sand every surface with 320 to smooth it out, and now I'm padding on the shellac, but with 8 carcases and 32 drawers, It's a real drag.

Advice? I'm using a Devilbiss regular gun with a 2qt pressure cup setup.

I'm starting to think the first step for me is to get more objective by starting to measure viscoscity. How many of you are measuring viscoscity, and if so, what cup are you using, and where can I buy one for a reasonable sum?

[Joe Jensen]

Some more information. The rough surface seems almost like it's caused by tons of overspray. Maybe it's time to give up the conventional gun.

[Dennis Peacock]

Joe,

What you need is lacquer retarder (normally 1 to 2 ounces per gallon) and also add some flow-out addititive to the lacquer. The sprayed lacquer is getting too dry to "lay down" wet, so you need an agent that will help keep the lacquer wet after it leaves the nozzle.

No flow-out additive? Then just thin 20% with thinner and add 2 ounces of retarder. If you thin too much you will fog the entire shop. DAMHIKT!!! :o

I've recently learned something new about lacquer. If you use a lacquer that has a banana smell to it? It's a lower quality lacquer. If you use a lacquer that has a vanilla smell to it? It's a higher quality lacquer. Jim Hagar taught me about that. Thanks Jim!!

[Joe Jensen]

Dennis, I think I'm thinning too much as I get clouds in the shop. Will thinning too much generate enough overspray to give me the rough finish?

[Tim Sproul]

Shellac is tough to spray with HVLP. I suspect with a conventional spray gun, it is even more difficult. Conventional shellac, because it is dissolved in ethanol (nearly everyone uses denatured alcohol which is ~95% ethanol), is difficult to spray because ethanol flashes so quickly. I find it sprays the best (I use HVLP) when I use very little air and only modest material delivery. I have to hold the gun a bit closer to the work too. With the amount of air coming out of a conventional gun, you're probably getting a lot more ethanol flashing off compared to HVLP.


Regarding your question about lacquer. I couldn't help. I'm new to spraying finish and really like the waterborne stuff. Especially considering I just do this for a hobby. I'd just let you know that a lot of different finishes (if you go by the finish chemistry, not the name on the label) go by the term lacquer....so buyer beware.

[Dennis Peacock]

Joe,

Too much thinning will for sure require some lacquer retarder to help it stay more wet while spraying. Here's something to try for your spraying technique:

1. Hold the gun closer to the work, about 4 to 5 inches away.
2. Move the gun slower and watch how the finish goes on from a slight viewing angle. It should look wet and fairly smooth.

Too much thinning will create lots of fog in the shop as well as it will tend to flash off quickly before the finish has time to "lay down".

Try the two things I suggested above and see how that does. I wish you were closer to me and I'd give you some retarder to put in it. :D

BTW, you can spray shellac with very good success, but you may have to use some "shellac wet" to help it get on the wood wet enough to lay down. Jeff Jewitt has it on his web site.

[Mike Furness]

The gun may not be atomizing properly, try taking the gun apart and cleaning it,or put in a rebuild kit.

Hey this is my first post here.Hello to everyone at sawmill creek

[Joe Jensen]

Thanks for all the tips. I am now convinced that I am thinning the NC too much. I'm also surprised that nobody else is using a viscoscity cup. I see that Jeff has one on his site for $10. I'm going to get one so I can get some more consistency. I'm also going to get a new gun setup from Jeff so I can switch to HVLP...joe