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"Airbrushing - thinners and cleaners." Topic

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Samulus30 Aug 2011 5:03 p.m. PST

I've come across so many conflicting views on this dotted around the internet I thought I'd try TMP – it never usually fails!

I basically want something to thin vallejo model colour to airbrush consistency.
Current theories seem to be:
Distilled water,
Acrylic Thinner,
Windolene/screen wash (something about ammonia content apparently…)
Airbrush cleaner,
or a various combinations of the above.

Can anyone give me a (hopefully) definitive answer? What should I use to thin my paints without breaking the bank?

Sundance30 Aug 2011 5:37 p.m. PST

I just use tap water and shake it up good.

McWong7330 Aug 2011 5:40 p.m. PST

I've never had any luck using VMC in an airbrush, but have yet to try the heavily diluted with water method suggested. I've gone as far as 75/25 water to VMC, but have been told it has to be much higher. Basically thin it all the way down and be prepared to do multiple coats to get a strong cover of colour.

Do not use thinners AFAIK.

ScoutII30 Aug 2011 5:45 p.m. PST

Not a definitive answer (to be honest…all of the above choices will likely work), but this is what I use for VMC and VGC through the airbrush




I have mixed my own in the past…but it generally isn't worth the effort IMO. I also prefer to use glass cleaner to clean glass…not to thin paints with (there are reasons for that as well…has to deal with the proper polymerization of the acrylic resin…or lack there of when ammonia and other reactive molecules are introduced…but I am sure someone will swear it is the best thing since sliced bread, so I will skip that). ;)

CeruLucifus30 Aug 2011 10:48 p.m. PST

I don't use Vallejo paints and I am a neophyte with an airbrush, but …

Vallejo Model Paints have an extensive FAQ which covers Airbrushing, though admittedly the short answer is to use their Model Air range for that.

Vallejo Model Paints FAQ: link

In general you want to thin paint with its approved thinner; for acrylics this is usually water. You would use other substances if this mix doesn't work. Examples: If surface tension is too high, add a flow aid. If you want the paint to dry quickly, replace some of the water with something fast drying, such as alcohol or ammonia. If after thinning the acrylic film isn't forming properly (you get thinner pigment on the raised areas, thicker in the depressions, as with a wash), you want to add acrylic medium. Etc.

Now as to the substances you mention,

Distilled water is just really clean water. Filtered water or drinking water may be suitable as well. The idea is to rule out your tap water from introducing chemicals into the mix you don't want, or calcium or other hardness minerals are affecting the paint or clogging the airbrush.

Bottled labeled acrylic thinner is probably thinned matte medium. For airbrushing you probably want Airbrush Medium, which is likely thinned matte medium with some flow improver.

Windex / Windolene / Screen wash is water + flow improver (= soap) + ammonia. Ammonia is a good solvent for keeping the airbrush clean plus it accelerates the paint drying. The main reason to use window cleaner though is it's cheaper than distinct bottles of airbrush medium + solvent.

Airbrush cleaner is a solvent for getting stubborn paint bits out of / off of the airbrush parts. Some of them are probably ammonia based although I've only used non-smelly ones.

Best of luck.

Personal logo Cardinal Hawkwood Supporting Member of TMP30 Aug 2011 10:53 p.m. PST

I use windex, window cleaner for everything , cleaning thinning etc throught the airbrush and even for cleaning real brushes and thinning straight from the pot..currently, in conjunction with my paintshaker I bring back to life dieing paint with a touch of windex and a solid shake..and I have been using it exclusively for about 5 years

Personal logo Cardinal Hawkwood Supporting Member of TMP30 Aug 2011 10:56 p.m. PST

and through an airbrush..40% thinner(windex) and 60% paint(shook for 3 minutes in a paint shaker{15,000 shakes}) works for me..

Personal logo Cardinal Hawkwood Supporting Member of TMP30 Aug 2011 10:59 p.m. PST
Personal logo Cardinal Hawkwood Supporting Member of TMP30 Aug 2011 11:00 p.m. PST
ScoutII31 Aug 2011 8:05 a.m. PST

plus it accelerates the paint drying.

drying ≠ curing

Might not make sense at first, but the acrylic starts to cure as soon as the catalyst shows up (depending on the formula, this might be something like oxygen from the air, UV light or some other stimulus that exists in the open environment…but not the sealed bottle).

Speeding up the drying time usually does not impact the curing time. Same goes the other way around for additives like PEG that slow the drying time. Once the process starts, it will continue till it is fully polymerized. In most cases faster drying isn't what we want, we want a faster cure. You also want the monomers to remain in suspension long enough to fully polymerize.

Bottled labeled acrylic thinner is probably thinned matte medium.

Thinning is not the same as diluting.

Not normally. Acrylic Thinner (labeled as such) has sort of gone the way of the dodo. People confused it with regular water (or some other compound). You now find things labeled as mediums, since it is a more accurate term. However, Acrylic Thinner (or in this case Airbrush Medium) is a monomer that has a lower viscosity than what you find in the undiluted paints. Generally speaking, it will be free of thinks like matting agents in order to avoid impacting the sheen of the paint that is being thinned (you would have quite a few upset customers if their high gloss candy apple red paint job dried flat because of a matting agent in the airbrush medium).

The main reason to use window cleaner though is it's cheaper than distinct bottles of airbrush medium + solvent.

The main reason is that someone back in the 1970s tried it and the world didn't end. They told someone else, who told someone else and the whole lot of them think they got a leg up on evil Big Paint who was trying to take them for a ride by selling specific thinners. Like I said, you can use it. The world will not end (and the paint will dry) – but that still doesn't mean that it is the right thing to use.

Anywho, when you thin a paint like an acrylic paint with something like water (or Windex…alcohol…Flow Aid…) you are diluting the paint. When you use a formulated compound like an Acrylic Medium you are actually adding a different type of acrylic resin into the mix that has better physical characteristics for the task at hand.

This is important because when a monomer like the acrylic resin actually cures it forms a bunch of long chain polymers that are sort of ball shaped. They have all kinds of hooks and what not that let them snag other long chain polymers that are next to them and when you have a few million of these chunky long chain polymer spheres all hooked together they form a very strong…very durable film. It can bend and move without cracking and does it's job wonderfully.

When you dilute the compound with something like water, you put fewer of the monomer molecules together. When they start to polymerize into the long chains, there will be fewer of those long chains close to each other and it will reduce the strength of the resulting film. You can see this yourself if you dilute the paint significantly and paint it on a surface. The resulting film is almost dusty like and you can rub it off quite easily.

Now the actual Acrylic Mediums are basically just a different formulation of resin (with other chemicals added to adjust drying times and the like). The resin used though generally will flow like water (though it isn't water). This provides additional long chain polymers for everything to bind to when it is curing. You can use something like the Airbrush Mediums I linked to above to thin the paint to the point where you can barely see the pigment at all, and they will still produce a durable film.

I know, you will definitely hear from people who will swear up and down that they thin their acrylic paints with only water (or only Windex…or some other substance they find in their medicine cabinet) but it will result in a less durable finish.

You can find a lot of information on the subject on trade websites like the American Chemical Society. Trust me, if the chemical companies didn't need to pay a bunch of guys in white coats to sit around and figure out how to get paint to flow well…they wouldn't.

If the price is too high on an actual airbrush medium, I would recommend looking at a cheaper acrylic resin that is formulated to flow well. Future is one of these, as are several varieties of acrylic varnish found at hardware stores (look especially at those designed for refinishing floors).

Evil Bobs Miniature Painting31 Aug 2011 10:07 a.m. PST

What Scoutll said; I use the Liquitex Airbrush medium and it works wonders.

Also, be careful using ammonia products in an airbrush. Often they have brass parts, and ammonia can corrode them:

If the parts were annealed you're fine. If not, damage may result.

CeruLucifus31 Aug 2011 3:52 p.m. PST

ScoutII thanks for that very informative post.

I did not actually mean to suggest not using airbrush medium but reading my post I can see now I give that impression.

I am new to airbrushing but use Airbrush Medium from Liquitex or Golden, or sometimes Future (not as a medium though as a spray varnish). This is because I came to the same conclusion you did about using Windex and the like, namely "somebody tried it and the world didn't end" plus "chemical companies wouldn't pay people to make this stuff if they didn't have to".

sunderland31 Aug 2011 4:25 p.m. PST

Don't Vallejo make their own airbrush thinner?

ScoutII31 Aug 2011 6:27 p.m. PST

Don't Vallejo make their own airbrush thinner?

They do (or something like one)…but I like to feel like I have a leg up on "Big Hobby Paint" and buy either Golden or Liquitex. You get a bottle that is somewhere around 50 times bigger for about twice the price as the bottle of Vallejo.

Not that I am against hobby paints I use a lot of them. However when it comes to things like this…I am a very cost conscience consumer.

I did not actually mean to suggest not using airbrush medium but reading my post I can see now I give that impression.

Didn't actually see it that way however, there were a few points to be clarified. There is a lot of misunderstanding when it comes to "water based" paints (almost as much as there is with "oil based" paints).

I don't claim to have all the answers, though I am pretty confident that the answers that I do have are on solid ground.

Samulus12 Sep 2011 10:06 a.m. PST

Thanks for all the replies guys, especially 'scout' who seems to really know his chemistry! (I couldn't stand chemistry, stopped it at GCSE).

I think I'm just gonna buy some liquitex, it seems that it does exactly what it says it does, and in the quantity that I need (not that much) it is cheaper than a future equivalent (don't think this is sold in the UK anyway).

What mix should I use, 1:1 medium and vallejo? or more medium?

Mitch K12 Sep 2011 11:03 p.m. PST

Liquitex airbrush medium.

Oh, and do NOT use ammonia. You read this in a lot of places, but it attacks the chromium layer on the interior of the brush, and will, eventually, strip this down and go into the underlying metal parts. This is NOT good.

ScoutII13 Sep 2011 6:12 a.m. PST

especially 'scout' who seems to really know his chemistry!

I know just enough to blow up stumps and mailboxes…any other chemistry knowledge is entirely accidental.

What mix should I use, 1:1 medium and vallejo? or more medium?

It is hard to give an exact formula. Unlike a lot of things, the paints we use will vary from batch to batch and bottle to bottle. You will also want to tailor it to your specific airbrush, as well as painting style. I like multiple thin layers most of the time – so I probably thin more than most. Using a commonly accepted point of reference – where a lot of people like to thin their paints to the point of milk…I probably thin to the point of skim milk when doing base coats. Usually takes two coats at that level for full coverage – though it dries fast and the second coat gets applied pretty quickly after the first.

The best advice that I can give in this regards is to pick up a bottle of the airbrush medium and an extra bottle of the paint you want to mix. Expect to use almost that whole bottle of paint. Now start playing with it. You will get different results with paints at different consistencies as well as (depending on your airbrush) you will want to learn how to use the double action as well as different pressures. Figure out how to get the fine lines and the broad strokes. Learn how distance will impact the pattern, and once you have all of that sorted you should have your answers.

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