Made a set of birch cabinets that turned out really nice and started to spray the laq. Noticed that the laq wasnt flowing right. It wouldnt flow. It built up nicely in the thick areas but didnt run out and “become one”. Also, when it dried it was …more of an range peel really than fish eye. What happened? Never had this happen before. In Flexners book it suggested silicon oil in the wood. Could not have been this. I wiped the sealer dust down with paint thinner..I think this is the culprit, but not sure. Was using a brand new gun with my airless. They still turned out ok but it was worth looking into…could have been worse. Conditions were great when I sprayed..low humidity, 60 degrees. I think I shouldve thinned it down more.
By the way. How is spraying poly…is it more difficult. I have a spray room in my shop so dust isnt a big issue. Never sprayed poly.
thank for the help.
Replies
There are a number of causes for orange peel. They all have to do with the finish drying before it has a chance to flow out and level.
First, make sure the finish is atomizing well. It should come out of the spray gun as very fine droplets. Depending on the spray gun, the finish will be atomized best somewhere between 6" - 12" from the tip of the spray gun. Keeping the spray gun this distance from the surface is important; too close or too far causes problems like orange peel. Also, you may need to increase the atomization air pressure, thin the finish, use a smaller needle/nozzle, or use an air-cap with more air-flow to break the finish into the tiny droplets (improve atomization).
If the atomization is good, but the finish is drying before it flows out, try these corrective actions; use the least amount of air to get good atomization for the fan width and fluid flow you're using (excessive air will cause the solvents to flash too quick), move the gun a little further away or a little closer (whichever is the case) to the surface to lay down a wet coat of well atomized finish, move the gun a little slower to lay down a wet coat, or add retarder (according to the manufacturer's directions) to slow the dry time.
Your spray gun (all spray guns) are set up to work with a specific range of finish thickness (viscosity). If you always keep the finish at about the same temperature (cold coatings are thicker) you can thin them the same amount every time to maintain a consistent viscosity. Use a viscosity cup to measure the finish and make a note of how much thinner it takes for that finish. In the future, you can use the same percentage with that finish.
Laying down a consistent wet coat is the second step to avoiding a lot of problems, including orange peel. You can use a wet mil gauge to measure the thickness of the finish as you spray and make sure it's thick enough, but not too thick. The manufacturer of each finish defines how thick you should spray their product; follow the guidleines for best results (in most cases).
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.
As far as spraying poly goes, it works fine as long as you have the viscosity adjusted for your spray gun. If you thin it, use naphtha instead of mineral spirits (for oil-base poly); naphtha evaporates a lot faster than mineral spirits and will help to avoid runs and sags. A drawback of spraying poly is it's slow dry time; the overspray remains wet and will adhere to everything it lands on. In place of oil-base poly, I'd use a waterborne poly like Super-Clear. It's designed to be sprayed and the overspray will be less of a problem.
Paul
This forum post is now archived. Commenting has been disabled