Thread: Surface tension patchy problem

G'day Arnold and welcome to the forum.

Not heard of droplets before, but I have seen a patchy surface where the finish appears to "run away" leaving a bare spot. Caused by contamination, often silicone, I believe in the trade it is called "fisheye". Panel beaters love (not) silicone car polishes for this reason. Some so called furniture polishes also contain silicone which causes massive problems when refinishing, I have also heard of woodworkers who have used sprays containing silicone on tools which has then transferred to the job in hand.

Not saying it is silicone but I would check the area you are spraying in, any rags, tools or surfaces which may have come into contact with some form of contaminant.

Thanks Bob, we have always kept anything with silicone out of this shed for this very reson, however, we'll keep a look out for anything with it as an ingredient. We're careful of latex gloves or anyone who has been near diesel. Hmmm.

This is product seems to always resist flowing nicely (giving orange peel texture) even when it's not showing this contamination problem (fisheye). we can haze it on lightly with several coats to smother any problem areas but we still have an ugly uneven orange peel effect.

Not sure if this will help but you mention orange peel and a quick search has revealed the following - hope it points you in the right direction. {it appears the pix didn't copy but I'm sure if you do a similar search you can pick them up}

Orange peel (effect)
From Wikipedia, the free encyclopedia






A photo of the Orange Peel effect on a car door. (Click for a larger photo)
Orange peel is a certain kind of finish that may develop on painted and cast surfaces, even screen protectors.[1] The texture resembles the surface of the skin of an orange.
Gloss paint sprayed on a smooth surface (such as the body of a car) should also dry into a smooth surface. However, various factors can cause it to dry into a bumpy surface resembling the texture of an orange peel. The orange peel phenomenon can then be smoothed out with ultra-fine sandpaper, but it can be prevented altogether by changing the painting technique or the materials used. Orange peel is typically the result of improper painting technique, and is caused by the quick evaporation of thinner, incorrect spray gun setup (e.g., low air pressure or incorrect nozzle), spraying the paint at an angle other than perpendicular, or applying excessive paint.
In some situations, such as interior house paint, the orange peel texture is generally desirable. In this case, a texture paint is generally applied with a spray gun. The texture is then painted over with the appropriate color. When painting walls, orange peel can also develop by using a roller with too little paint or too thick a paint and the surface dries before the texture can level.


ORANGE - PEEL EFFECT

DEFINITION
Poor surface texture of the paint similar to the surface texture of an orange skin.

CAUSES
Spray gun held too far from object.
Spray pressure too low (poor atomisation).
Paint film too thin.
Viscosity to high.(paint too thick).
Hardener and/or thinner too fast for the conditions or size of object.
Spray nozzle too small.
Flash-off time too long between coats.
HOW TO AVOID
Keep spray gun within the recommended distance from the object.
Ensure spray pressure is as recommended.
Always apply wet coats.
Adjust paint viscosity as recommended.
Choose correct hardener and thinner (> temperature table).
See tech data for correct choice of spray nozzle.
Allow a long enough flash-off between coats.
REPAIR
If the problem is only slight, sand down with P1200, polish with Glasurit Fine Polishing Paste 562-1602 and finish with any standard deep gloss polish.

Thanks for your help, Bob. It looks like spray pressure and a bit of dilution makes the difference. The manf. Rep. came up with some ideas, pressure should have been about 8 psi instead of 20. We should have thinned with about 15% of water while we used less than 10.
our next experiment was to spray with these parameters over twenty contaminates we could find in our shed. ....Perfect finish over everything!!!

Thanks for the feedback. I'm pleased you have achieved a good result.