Replies

1. 
   PlaneWood | Apr 30, 2004 03:04am | #1

   No.  Orange peel is caused by microscopic contaminants on the surface.

   I presume your using lacquer?  If so, I would do one of two things.  Put a couple of coats of lacquer sanding sealer on that has been thinned 50% with lacquer thinner.  Lightly sand with 400 grit paper between these coats.  Or, put on a couple of coats of a 1# cut of dewaxed shellac.  After the last sanding, clean the surface real well and spray the lacquer with the first couple of coats thinned about 25%.  Last couple of coats full strength.

   If using varnish or poly then thin it about 50% and put on 2 or 3 hand wiped coats.  Lightly sand between each coat.   Clean the surface real well with a rag damp with mineral spirits and finish the spraying.

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)
   PlaneWood

1. 
   Tao | Apr 30, 2004 04:01am | #2

   Mike, I think you are confusing orange peel with fisheye.  Fisheye, or crawling, is caused by surface contamination. Orqange peel is simply the failure of a finish to level properly, and has a number of causes:

   Wrong thinner. The wrong thinner, especially cheap ones, have the wrong blend of solvents (usually to fast, or hot)  and won't let the finish level properly.

   Dirty air cap or fluid tip.

   Too much air pressure or holding the gun too close to the surface causes one kind of orange peel because the air actually blows the finish into a pebbly texture.

   Holding the gun too far away or with too high a pressure can cause too much solvent loss while the material is in the air so that it is too thick to flow out properly when it hits the substate.

   Too thin a coat flashes off to fast to level out properly.  Most furnitue clears need to be applied at 4 to 5  wet mils.

   Too high a viscosity or too small a fluid tip on a siphon gun can cause not enougjh material to flow, resulting in a starved finish which will look pebbly.

   There are probably a couple more causes that I am forgeting.

   Cures, in order of application:

   Make sure your fluid tip and air cap are absolutely, surgically clean around any and all orifices.  Use a magnifying glass to make sure.  Use a brush and a toothpick to clean.  don't put any metal in any orifices, no matter what the temptaion.

   Always use the thinner that the manufacturer recommends for the coating you are applying.  Poor quality thinner is a very common cause of problems with lacquers.  I don't now what finish you are using.

   Get a viscosity cup (still under $10, I think, from homestead finishing), and make sure your viscosity is within te range recommended for your gun, air cap, and fluid tip combination.

   Get a wet mill gauge (should be free from any paint store that caters to professionals) and make sure you are getting enough material down.

   With an HVLP gun, hold the tip 6 to 8" from the surface, and square to it.  Some manufacturers recommend a little more distance, but never less.

   Use just enough atomizing air to get the atomization you need to make the finish lay down properly.  Overatomizing just wastes material and causes problems.

   If you will do these steps, in order, you will have about a 98% chance of solving your problem.  I've done a lot of troubleshooting on finishes, and this almost always does the job.  There's a chance that you might have a damaged air cap or fluid tip, or that you just have a lousy gun.  I've seen some cheapies that would hardly even spray water well.

   The main reason to change fluid tip and air cap is to get more or less material down.  It's pretty hard to spray heavy bodied material with a tip that's sized for water thin materials, and you don't get very good control on thin bodied materials when your tip is the size of a firehose.

   I vastly prefer any kind of pressure feed to a siphon feed, especially with HVLP.  Pressure guns are so much more responsive, use a lot less air, and you don't have a breather hole to clog up ( another thing to check.)

   Hope this helps.

   Michael R.

2. 
   Paul_Snyder | May 01, 2004 12:05am | #3

   It may solve the problem. There are a number of causes of orange peel as Michael pointed out and too large a needle/nozzle is a common problem. Here's a list of other sources and solutions for orange peel;

   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.

   Paul

1. 
   user-5880422 | May 01, 2004 04:07am | #4

   Paul,

   this is one of the best troubleshooting posts I have seen, too bad we can't make it a "sticky" for easy reference in the future.

   Edited 5/1/2004 1:30 am ET by Jeff

1. 
   Paul_Snyder | May 01, 2004 05:24pm | #5

   Thanks Jeff. :)

   It's an excerpt from a chart I'm putting together for troubleshooting spray finishing problems on my website. The website is a very slow process for me but eventually I'll get it together.

   Paul