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#1
09-08-2019, 08:35 PM
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Are stearates in sandpaper really an issue?
I'm trying a new waterborne finish and having trouble with craters forming as the sanding sealer for the finish dries. (I haven't even gotten to a top coat yet)
The sanding sealer seems to spray beautifully, but as it dries, there are areas where the finish looks like it's running away from certain areas. I've read this problem can be caused by stearated sandpaper, but I've also read that stearates really aren't a problem. I've tried wiping after sanding with a 50/50 mix of alcohol and water, but to no avail. I'm curious to know what others use for between coats sanding and opinions on whether or not stearates really cause problems. Any info is appreciated. 
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#2
09-09-2019, 12:17 AM
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I've never had sandpaper cause that problem in 30 years of finishing.
Have you sprayed WD40, any kind of oil based product, silicone or any type of aerosol lubricant in the area recently? Spraying stuff like I've listed here even in an adjacent room can float in and ruin the piece to be finished. When one coat of finish becomes contaminated, succeeding coats will show similar problems.
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#3
09-09-2019, 02:24 AM
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My paint booth is upstairs in our building, I used some silicone spray downstairs in our cnc machining area (room under paint booth) and the next day my paint jobs had fisheyes, my booth has got inlet filters and everything.
The area between upstairs and downstairs is a solid ceiling, the misting of the silicone still managed to damage my paint work. Steve
__________________
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#4
09-09-2019, 05:27 AM
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I haven’t sprayed any silicones in the area recently, probably not in years, but it does describe my problem. By the way, the problem seems to worsen with subsequent coats. The first coat levels beautifully. The second coat has a couple of craters that are easily sanded out. Subsequent coats get worse, especially if applied heavily. Steve, how did you resolve your problem?
Does fisheye remover work? I’ve read that fisheye remover is actually silicone and condemns the user to use it forever. There must be a better way, right? By the way, I can spray shellac with no problem. Last edited by Quickstep192; 09-09-2019 at 05:34 AM.
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#5
09-09-2019, 07:17 AM
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I have never had fisheye that I could confirm the cause to be stearated sandpaper. I don't prefer fisheye eliminator, so I deal with fisheyes by spraying lighter coats, or by drop filling if the craters are not too numerous.
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#6
09-09-2019, 11:19 AM
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Strip it and then use shellac for a sealer. Spray a few light, misted on coats.
__________________
"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon
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#7
09-09-2019, 03:14 PM
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Quote:
The first test is the top coat applied over their waterborne sanding sealer. The second test is the top coat applied over shellac. I haven’t even started with the top coat and it already looks like shellac is the better sealer.
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#8
09-10-2019, 07:21 AM
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Quote:
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#9
09-10-2019, 08:41 AM
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Target sells a shellac-based sealer intended to be used with its waterborne finishes. I tried it, but found that it was quite dark in color, not the look that I wanted. I wanted "water white".
A potential downside to using shellac as a sealer is the color that it provides. Depends on what color you are after. Even the lightest shellacs impart an amber hue.
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#10
09-10-2019, 10:51 AM
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Quote:
is usually beneficial to a waterbased finish's appearance, since they tend to have a naturally coolish look and a bluish cast, IME. Perhaps there are exceptions.
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#11
09-10-2019, 12:40 PM
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I actually like the amber hue, so shellac won't be a problem for me in that regard.
As a side note, I recently got powdered clear shellac from a company called Weller Mart. It is as close to clear as anything I've ever seen and it's powdered, so it dissolves right away. I too found the water based sanding sealer to be quite dark. Perhaps not objectionably so and it may look different if I were ever able to top coat it. I may never get to find out since it looks like I'm going to abandon the water based sanding sealer test.
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