Replies

1. 
   Paul_Snyder | Apr 04, 2004 04:19pm | #1

   Jake,

   I don't like to use retarder unless I really have to. It slows down the dry time of the lacquer and makes it more susceptible to dust nibs. There are a number of causes for orange peel; though a very slight, almost imperceptible orange peel is normal; look closely at a car's factory paint job and you'll see it.

   Here's a list of common sources and the fix;

   Cause

   Description/Solution

   Needle/Nozzle wrong size

   Select and use the correct needle/nozzle size based on the coating you are spraying. The spray gun manufacturer/supplier and/or the coating manufacturer/supplier can recommend the best size. Generally, a smaller needle/nozzle atomizes the finish better but reduces fluid flow and fan width.

   Insufficient air pressure/volume

   Adjust the atomization air pressure to the minimum setting needed to produce a fine spray. Too little atomization air pressure will produce larger droplets and a center-weighted spray pattern. Too much air will produce excessive overspray, dry spray, and/or the finish will dry before it flows level. Make sure the compressor supplies enough air, in cubic feet per minute (CFM) for the spray gun you're using.

   Viscosity of coating

   Thin the finish, as needed, to achieve the proper viscosity. Properly thinned, the finish should atomize into tiny droplets that flow out and level. If the finish is too thick, it will spray in larger droplets. If it's too thin, you will get sags/runs unless you spray very thin coats.

   Fluid flow

   Adjust the fluid flow to get the best atomization at the current air settings. Too much fluid flow for the amount of atomizing air will result in large droplets (poorly atomized). Too little fluid will dry before flowing level.

   Spray gun distance/speed

   Maintain the recommended distance from the spray surface. Depending on the spray gun and settings, a constant distance in the range 6" - 10" inches is generally best. Maintain a steady hand speed during each spray pass, from end to end, that lays down an even wet coat in the thickness range recommended by the coating manufacturer. Use a wet mil gauge to measure the wet film thickness.

   Envirnomental conditions

   In hot weather, the finish can dry before flowing out. Use a slower evaporating thinner (retarder). Excessive air flow over the sprayed surface will cause the finish to dry before flowing out. Avoid strong air current over the drying surface.

   There's some information on measuring viscosity and wet film thickness at this link - Viscosity & Wet Mils. There's a link in the article that covers spray patterns for a variety of surfaces.

   Paul

2. 
   TomT226 | Apr 04, 2004 04:47pm | #2

   What temp and humidity is it when you're spraying?

   What kind of surface are you spraying?

   I don't normally use sanding sealer on NC jobs because it can cloud the finish. Generally the first 3 coats show slight OP. Successive coats (thin) will normally remove this. A flash coat of 50/50 will remove most any other surface blemishes. Colored lacquers tend to show OP and defects worse than clear. Shoot a couple of coats of clear over it if you are using the colored lacquer. I use run of the mill lacquer thinner, and have never found any problems. I generally shoot Deft or Parks.

3. 
   jazzdogg | Apr 04, 2004 07:41pm | #3

   Jake,

   A little orange peel seems inevitable, but, in my experience, it's a little worse with an HLVP rig than with a conversion gun. In either case, rubbing out is important if you want a smooth, glassy surface.

   Good luck,

   -Jazzdogg-

   Whether you think you can, or you think you can't, you're right.

4. 
   PlaneWood | Apr 04, 2004 08:17pm | #4

   Try undercoating it with a 1 lb cut of dewaxed shellac.  Put on a couple of coats then lightly sand with 220 grit paper or 0000 steel wool.

   In my experience, orange peel with lacquer is caused not by how your spraying it on but by what it's going onto.  The shellac will help provide a more even surface tension for the film.

   I use Deft brand lacquer. It is advertised as a brushing lacquer, but I have always sprayed it.  It is slower to cure and very forgiving in hot humid climates like Houston.  I used to use lacquer sanding sealer as an undercoat, but have found I like the results better when using dewaxed shellac. 

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)
   PlaneWood

5. 
   OneofmanyBobs | Apr 04, 2004 09:46pm | #5

   Yes, there are flow-out additives.  The anti-fisheye additives do about the same thing.  Note that these are the dreaded silicones  (more properly "silanes").  Not all silicones are the same, just like not all solvents and oils are the same.  To get rid of fisheye caused by silicone contamination, they use more silicone.  Just a different kind.  Check with the manufacturer of your lacquer and use the brand of flow-out additive that they recommend.  Solvents do not achieve the same effect.  A slight orange peel is almost inevitable.  Due to variations in electric charge on the surface.  Additives may improve it for you but are not likely to eliminate it.

1. 
   sneezy | Apr 05, 2004 05:06am | #6

   First, I have to say that I hope you guys fully realize what a great help it is to someone like me, attempting to learn a new skill, to have people like you taking time to pass on your extensive knowledge. Paul I read your articles before I started and got a wet mil gauge and viscosity cup; great help.

   Temp in my shop is 65 to 70. Don't know the RH but I do know its extremely dry up here.

   It seems, from all your comments, that I may not have as big a problem as I thought, which is a relief. The orange peel is very slight and smooths out quite easily with 4-0 steel wool. However, I have to thin about 60/40 and spray about 2 mils. Any thicker and things start to get messy. Is 60/40 too thin? The instructions for my lacquer says to thin 15%. 50/50 gives great results but I imagine that really is getting too thin for every coat.

   Once again thanks.

1. 
   DonStephan | Apr 05, 2004 05:51am | #7

   I use water base instead of solvent, but saw a brief mention in Jeff Jewitt's new finishing book on "flow coating".  If I remember correctly, after about 3 "normal" coats of NC and sanding, final coat is thinned 50% with solvent to get smoother finish that is close to a rubbed out finish.

2. 
   TomT226 | Apr 05, 2004 02:21pm | #8

   Even using Deft, (which I like) I've found that you generally get more orange peel when the RH is low. Like "Planewood" I sometimes have to spray in high humidity environments, but during late summer it gets much dryer.

   I've used "flash coats" thinned as much as 80% when the humidity was low, and had the problem. The "flash coat" just melts the surface and allows gravity to smooth out the imperfections. Watch the vertical surfaces where it will run if you get a heavy coat.

   After you finish this project, do some tests using the same settings you have now on some close grained wood like Maple. Shoot a couple of coats unthinned for your sealer, then a couple thinned 50/50, then a flash at 80/20.

   In my experience, you shouldn't ever have to rub out flat, or semi-gloss NC lacquer. Gloss lacquer, as on piano finishes, may need rubbing.

   Let the "flash" do the work for you.

1. 
   PlaneWood | Apr 05, 2004 03:02pm | #9

   Tom -

   One rainy day here I flash coated (over the last coat of lacquer) with pure retarder.  It worked.   I had sprayed the lacquer the night before and came out the next morning and saw that it had blushed.

   A retired Ethan Allen refinisher here in Houston told me once to always have air moving over the piece when spraying lacquer.  I have found that to be great advice to prevent blushing.

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood

1. 
   TomT226 | Apr 06, 2004 01:41pm | #11

   Exactly. I always have a couple of floor fans running on low in my drying area keeping the air moving. Keeps most of the damn nits outta the finish too.

3. 
   Paul_Snyder | Apr 06, 2004 02:18am | #10

   Jake,

   If you have to thin 50% to get good atomization, then go for it; there's no problem with spraying thinner coats with solvent lacquer. Depending on your spray gun, you should be able to get good results with more air pressure and less thinning; fine atomization and a continuos wet coat are key to a smooth finish.Paul

4. 
   SEBDESN | Apr 07, 2004 02:56am | #12

   More thinner....You might have to put on more coats, but thin it till you don't get the problem....automotive  laquers are(or used to be) thinned 150% routinely....

   Many problems are caused by the VOC requirements of the finish you are using...

   That does not  keep you from thinning as much as you need to get a good finish...They are bound by law to tell you to only thin "X" amount so the stuff still meets VOC requirements...But...You can thin however much you want.... 

1. 
   TomT226 | Apr 07, 2004 02:27pm | #13

   Hmmmmm.....how do you thin 150%?

1. 
   SEBDESN | Apr 07, 2004 05:43pm | #14

   10 oz of finish 15 oz of thinner

6. 
   WorkshopJon | Apr 08, 2004 08:55pm | #15

   	17187.1
   	Is there something other than retarder that can be added to NC lacquer to improve flow out when spraying with an hvlp gun?" Jake, If you thin with an industrial (automotive) type thinner designed for very high temps, that WILL solve your problem.  IMO, better to use a slower evaporating thinner, and less of it, so it has time to flow out without reducing the surface tension of the lacquer, rather than more of a faster evaporating one. Over thinning reduces both gloss and flowout. I use PPG DTL105 for those situations.  Rated for use between 95F to 115F.  Try it.  just don't over thin, or you'll get runs and drips. I typically use it at ~72F. Jon