by Carol Williams
(edited from a series of emails)
Have you ever pulled a can of matte spray, shake it, then spray, only to find white speckles on your horse? What causes it? Can it be prevented? What can you do to resolve things?
Yes, I've had this happen. And I'm not sure exactly why. I think the answer is somewhere between:
I just had this happen this week, as my local chain store no longer carries my favorite matte, and I had to try another. Yes, it was on a "test" horse (as it always has to be anymore for every single can, due to this very thing happening often enough).
I have set the darned can aside for now as I haven't had a chance to fully "test" the problem (or find a fix).
Ok, since this very thing happened here earlier this week, and it's happened often enough to be aggravating, I thought I'd go ahead and do some experiments and see what happens.
I was able to successfully create the "frosting" effect the first try.
"Tree House Studio" brand "Matte Coating" from Hobby Lobby. (I will note, that the same "frosting" effect has occurred with almost every brand I've tried over the years at some point... and that's well over 20 different products... however, I will say that some products may be more prone to this than others)
Test subjects: pieces with *oil paint* on them, and a factory painted section of a breyer.
To see if I could get it to happen, I took the can (new) didn't shake it up, and a spare breyer . My shop is *cold*. The indoor thermometer reported 51F and an outdoor temperature of 23F.
This will assume that both the can and the model were around 50F. I took them outside to spray them.
Result? Instant and **severe** frost. Far worse than I'd encountered earlier this week. It's colder out as well, so that leads me to suspect that cold is the issue.
I put the can in a pan of warm water, and a thermometer touched to the can later reported 82F.
I sprayed this on a test object both indoors and out, and had **no frosting**. The body was the temperature of my shop (about 50F). I left the model outdoors for about 10 minutes (to cool further) and tried again, and did not experience frosting... (but, I wouldn't necessarily trust a 30-40 degree model not to do so).
While I'll need to let the can cool awhile to try cold spray on a warm body, I don't know what results to expect and probably isn't necessary to further establish how the frosting occurs.
I'm going to say, to be safe:
Now, for the "fix" part... this was interesting and isn't 100% reliable.
The test piece from last week (oil painted) where the frosting had a chance to dry/cure for a week proved to be more difficult to fix, than the test items I worked with today. So, if frosting should occur, try to get the can/object warmed sooner and fix applied, for better results.
Initially, I tried using solvents to help. They all did... until they redried. These included alcohol, acetone and paint thinner.
What actually did make a difference? Warm body, warm can, and respraying over the frosted areas. The spray had to be a bit on the "heavy" side (which makes it tricky, to try to avoid drips, sags, runs). Keep in mind such sprays are solvent-based, so the solvent in the can will partially or completely dissolve spray that was already applied. (not sure which one it is, but I don't have any of it on hand regardless) I could see the frosting "dissolve" into the new spray in a few seconds. Some areas needed more spray to do the trick.
The "well dried" piece was more difficult, and required several coatings in places.
I also tried gently rubbing the surface of the frosted area first, with the tip of a dampened q-tip. This did seem to remove a little of the frosting, but not a whole lot on it's own, except maybe where it was very faint to begin with. I let the area dry, then coated it with the warmed can of spray. This seemed to help.
I'm still letting things dry and cure, and I can see a little "haziness" re-developing here and there, although it's very much muted compared to what it was. I did try swiping a little bit of acetone with a very soft shader over the affected areas, and that seemed to help (although it does want to introduce a little "texture" in that spot. I spritzed over this area again a couple times with the warmed spray.
The problem with the fix is that when you're doing your clear-coating, chances are you're doing it right on top of paint. So any sort of rubbing with a q-tip may well rub off some color and cause a new problem. Additionally, any "light swiping" with a soft brush and acetone (or anything else) is also likely to lift a skim of paint off the surface. This is going to be even more of a problem with oils on models that are not completely cured (having sat around and dried a month or more).
So, one must be prepared to have to touch things up later, or just repaint the piece... just in case. (Or turn it into an app or paint).
Chances are, if frosting is going to occur, it's going to happen right from the first spritz, so STOP right away. The less there is to fix, the less hassle it will be, and more likely the fix will be successful. Get the objects warmed as soon as possible, then reapply over the top for best results.
The tests were *not* done on acrylics, so I can't say how well any of the fixes work on that type of paint. Keep in mind that a heavy coating or soaking of some clear-coats on top of acrylics (particularly white or gesso) can sometimes result in the clearcoat soaking up *under* the paint and discoloring it or worse... so go carefully, and test a leg or something first.
All of this may be relevant to any spray products you use, including primer.
I hope this little experiment helps some folks here!
This "Tree House Studio" stuff... ends up flat rather than "matte". It does seem to be less expensive (and in bigger cans) than Dull Cote, although I don't know if it would have all the same properties for Dull Cote's various uses. I'll probably find out eventually!
As to the Krylon-- I have not been happy with their "matte" for quite some time, and gave up on it entirely (due to it's gummy/sticky feel when "dry").
However, a couple of years ago I called Krylon about this, and they sent me sample cans of a number of things... the Artist's Matte, Regular Matte, and Flat. I couldn't tell the difference between the matte's, I'm not sure there is one, and the "good stuff" in the samples was no different from the goo they sell on the shelves. But the flat was FLAT, and worked well when I wanted flat (like Dull Cote) and of course in a larger quantity and better-priced. It wasn't sticky/gummy either. However, I've not had a bit of luck finding Krylon Clear Flat in any store, and wasn't able to locate a source online either.
The best Matte I liked is "Design Master" brand, Clear Matte-- it's not flat, it's not "semi-gloss" or "satin" (like so many clear mattes end up to be). I was getting it at Hobby Lobby in their woodworking section... but alas, they've discontinued it. It can be found at various outlets online though.
And yes, this Design Master frosted once on me too, a long time ago. After today, I'd bet it was because the can was cold :) Other than that, no problems with the product.
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