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These are in addition to the fact that the spray gun is out of tune.
I wrote about the problems earlier caused by your spray gun. Just because your gun is well tuned doesn’t necessarily mean you’ll always get good results. Other things can go wrong. Here are five of the most common.
The biggest, of course, is the orange peel. It is not possible to completely avoid this defect, but it is possible to get so close that the defect is not noticeable.
Orange peel can show up in any finish and is usually caused by spraying too thick liquid with too low air pressure. Put this way, the solution is obvious: diluting the liquid or increasing the air pressure.
If you are using a spray gun with air supplied by a turbine rather than a compressor, you will not have much control over the air pressure; you will probably need to dilute the liquid.
Another cause of orange peel is holding the gun too far from the surface or moving it so fast that it doesn’t deposit a completely wet layer. The best way to determine the correct distance and speed is to observe what is happening in a reflected light.
By arranging the lighting and positioning yourself so that you can see a reflection on the surface you are spraying, you will see when the finish is not proceeding properly. Then you can make the necessary changes.
Dry spray is an overspray that settles on the surface after the finish drops have dried in the air. Dry spray produces a sandy look and feel and most commonly occurs at the edges of a spray pattern when the finish dries too quickly. It also occurs when the finish bounces off the surface and then settles on it after both the finish and the bounce have started to dry.
Dry spraying only occurs with quick-drying finishes and is especially likely to occur when spraying the interior of cabinets, boxes and drawers where there is more bounce and turbulence.
The obvious cure for dry spray is to slow down the drying of the finish by adding a retarder, which is a slower evaporating thinner. Since finishes that dry faster with paint thinner, the appropriate retarder is paint retarder.
The retardant lacquer can also be used with shellac if you want to slow down its drying. Xylene can be added to the conversion paint to slow drying.
Don’t add more retarder than necessary, however, or you could extend the drying time so much that the finish will collect dust and show print marks for hours or even days.
Redness is a spray problem because it only occurs with fast-drying finishes that are diluted with lacquer thinner or alcohol. Redness does not occur with water-based paints or finishes that are brushed.
The milky white of the redness is caused by moisture in the air that condenses in the finish and then, upon evaporation, leaves air pockets that refract the light and prevent it from traveling through the finish. Discoloration is more likely to occur, of course, in humid weather.
Conversion paint rarely blushes, and oil, polyurethane, and water-based finish paint never blushes (although the water-based finish can become a little dull when applied very often).
To avoid blushing in lacquer and shellac, add a lacquer retarder to the finish before applying it. The retarder slows down the drying process so that the finish can still compact and eliminate air gaps after the moisture has evaporated.
The disadvantage of adding retarder is that it slows down the overall drying of the finish, which slows down production and could lead to problems with dust, runs and print marks. For this reason, do not add more retarder than necessary to avoid redness.
If you blush and it doesn’t come out on its own within a couple of hours, spray some retarder (as little as possible to lighten the finish) on the surface to “open” the finish and let it compact solid and eliminate gaps. Spraying regular lacquer thinner (or rubbing alcohol on shellac) can work even on a drier day. You can also scrub the finish with steel wool or an abrasive pad to remove the finish closest to the surface, where the redness occurs.
The finish does not harden
There are two causes for the finish not hardening within a normal amount of time. The first is that you have added a paint retarder to solve one of the problems described above. The second and most common is that you are working in a cold environment. Either way, the finish will easily show print marks.
Low temperatures slow down the drying of any finish. Only finishes that are diluted with paint thinner can be adjusted to dry normally under these conditions. The way to do this is to add some “quick” or “hot” lacquer thinner to the finish to make it dry faster. These paint thinners are generally available at auto body supply stores. You can also add acetone, which is widely available. If you live in an area that complies with strict VOC laws, you can switch to 275 VOC hairspray, which is made with a lot of acetone.
Poorly coated edges
Not getting enough finish on the edges of cabinet doors inevitably leads to peeling, especially under sinks. Inadequate construction on the edges is a spray problem because it rarely happens when brushing a finish.
You have to be fully aware of the problem to avoid it, but once you are aware of it, avoiding it is easy. It’s just a matter of spraying full coats of finish on the edges, holding the spray gun at a right angle.
Many pavers hold the spray gun at a 45 ° angle when spraying the edges and this does not deposit enough finish. The end user will start experiencing problems within several years.
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