acrylics and airbrush question

I just did some airbrush work with the XtraCrylics paints from
Hannants. All seemed to be well, until the next morning, when I
noticed extensive cracking of the paint (isn't that called orange
peel?). I've never used acrylics before, so chances are I just doing
something wrong. Here what I did:
First I washed the kit with soap and water, to create a clear surface.
Then, I sprayed on four layers of paint, with about 45 minutes between
each pair of layers.
Now, I'd read someplace that several layers in quick succession were
OK with this paint, and in any case, that's what I usually do with
enamels.
Does anyone have a guess what went wrong?
Rob
Reply to
Rob van Riel
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Reply to
Serge D. Grun
If the layers of paint were thick(ish) then that is almost certainly what caused the problems. I've had that happen with Xtracrylics.
I find that if you spray on a mist coat of the required colour, then it will dry within less than a minute. You can then spray on another mist coat in the same session, and again. I normally then allow the paint to dry for two or three hours, before repeating the procedure. I have had some very good results with Xtracrylics using this technique.
Another thing to note is that if you spray Xtracrylics directly onto a gloss varnished surface, they just will not cover at all well. The technique then is to apply single mist coats with at least two hours between them, until you get the required colour consistency.
And another thing... The Xtracrylic RLM79 Sandgelb comes out *orange*. Give this one a miss. The other colours that I have used (RLMs 02, 04, 65, 66, 70, 71, 74, 75, 76, 78, 80, 81, 82, 83, Dark Green, Dark Earth, Sky) are all a good colour match, but RLM23 red really requires a dark undercoat.
Reply to
Enzo Matrix
This is bad, very bad!
First off you are not experiencing Orange Peel. Orange Peel is an effect where the paint does not level correctly. If you shine a light on the surface it appears to have a texture like an orange.
Now the Cracking. I had cracking problems with Gunze with Future as an over coat. My solution was to chuck using Gunze and Future together. I believe your problem is you did not wait for one layer of paint to dry before applying a completely fresh layer of "wet" color. Try letting one coat dry for 24 hours then apply the next coat and see what the results are.
BTW Enzo Matrix... I love the handle!
Reboot!!!!!!!!!!!!!!!!!!!!!!!!
Cheers, Max Bryant
Reply to
M Bryant
Actually, to give a more complete answer, which I did not have the time to do in my previous post, acrylic paint is an emulsion of acrylic resin in a water and/or alcohol-based carrier. Just like any resin, it needs to polymerize once the carrier has evaporated. Hence, acrylic paints will _dry_ quickly, because it doesn't take much time for an alcohol-based carrier to evaporate, but will need anywhere from 1 to 24 hours to _cure_. The actual curing time depends on the acrylic resin being used, room temperature and hygrometry. It is also likely that the layers were too thick and/or the paint wasn't thinned enough.
Reply to
Serge D. Grun
No, that's not orange peel. OP looks like the surface of an orange.
I think you waited too long between coats. After 45 mins you coat is mostly dry; applying another coat results in cracking. hth
The Keeper (of too much crap!)
Reply to
Keeper
Acrylics have very finicky recoat windows. Polly Scale, MM Acryl, Aeromaster and Gunze flats can be recoated as soon as they've "flashed off" and up to another 15 minutes or so, after that time is up wait at least an hour. I find Gunze satins and glosses to need over night before recoating. Tamiya flats are similar to the first set but they don't do well with more than two coats, I hate Tamiya glosses so can't say for them. It sounds like Xtracrlyics are behving like Gunze satins or glosses and need to cure before recoating.
What happens is the first coat dries and shrinks a little from losing the water or lower alcohol carrier, then it starts to cure and the surface becomes impermeable to the tail solvent (glycol ether or a higher alcohol) and the second coat dries, starts to cure, shrinks, etc.....eventually the bottom most coats finally finish curing ans shrinking and gracture the film of the later coats.
Reply to
Ron
I don't have a direct experience with Xtracryl but a lot with other acrylics and I think you are right.
Acrylics dry quickly, but to fully cure you must wait at least 24 hours to be safe. So either you spray another coat in 10 minutes or so, or you'd better wait several hours (one day is better).
Btw, 4 coats seem a little excessive to me: 2 are usually more than enough (of course it depends on how much you thin the paint).
You can put more coats to have a high gloss finish, but that's another story: spray a light mist to give some tooth, wait a couple of minutes and spray a heavier one, then wait 10 minutes and spray a really "wet" one (just stop moments before the paint starts to run). All 3 coats must be sprayed in 30 minutes or so: the top coat can dissolve the underlying paint just a bit so you have a really smooth finish, but if the paint has already started to cure (after 30 or so minutes) the paint can crack because acrylics shrink as they dry.
Also test paint/clearcoat compatibility on a scrap model (always use plastic, not paper or cardboard): for example Gunze is not compatible with Future and PollyScale flat (it will crack every time, no matter how long you waited), while the PollyScale gloss clear seems to work (or maybe the cracks are so small you can't see them...)
I found that a good and safe clearcoat for Gunze is the old superscale/microscale set (gloss/satin/flat).
Hope this helps.
Reply to
Yuri

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