Thinning paints for airbrushing

[kashirigi]

I recently (as in last week) made the purchases of a double-action airbrush, a compressor and a portable spray booth. I'm pretty happy with it so far, but one thing has happened which I found somewhat odd.

Many sites (I'm certainly not going to list them) suggest thinning your paints with isopropyl alcohol. I've never had good results with that, but thought I'd try it again, just because of the overwhelming weight of opinion.

A quick word; I'm not using Tamiya paints (mostly because I hate the way they smell). I'm using Golden Artists' acrylics.

Anyway, mixing the alcohol with paint had the weirdly perverse effect of making the paint seem thicker. I added a huge amount of alcohol until it was airbrushable, then tried it out. And by huge, I mean it had to be something like a 4-1 ratio of alcohol to (liquid) paint. Naturally, this was a huge error, and it took nearly an hour to clean out the nightmarish mess left inside my airbrush. It was like putting sticky sand through it, and the paint stuck to everything and clogged the nozzle every time it sprayed.

Has anyone else seen such a weird thickening on adding alcohol?

On the plus side, thinning the paint with water and Golden airbrush medium seems to work just fine. However, the airbrush medium is full of retarder, so if you do the recommended 50/50 mix the paint will take forever (and I mean hours) to dry.

That's why I tried the alcohol.

So, in a nutshell:
Alcohol=NO!
Straight medium and paint = not really
Mostly water with some medium = OK!

[inrepose]

Aha! Hopefully I can help here. I suddenly feel useful

I have no experience of the Golden artist acrylics but what I do know is that acrylics don't always like Alcohol. Tamiya is the exception because the stuff is perfect when mixed with "Isopropyl alcohol". I am not sure if you have used isopropyl but it is certainly the choice of thinner for Tamiya color.

However.. After years with Tamiya I was recommended by a pro-tank modeller to switch to Vallejo model air. Vallejo is amazing! Rather than fussy thinning ratio's with Tamiya (which sometimes resulted in paint so thin it ran off the model or paint so dry it went on like a crumble.

Vallejo have their own thinning agent which you hardly need to use because the model air paints are already ready to spray - you just shake them and poor directly into you airbrush pot.

I thought I would end up with a lower quality finish when I stopped using Tamiya but the result was a rock hard acrylic finish that you can't scratch off. They also don't smell as bad because you don't use the alcohol, so there are some potential health benefits.

The other important airbrush tip is pressure. I would not go much above 25psi because any higher will dry the paint particles mid-air and you end up with a sand blast of tiny rough crumbs. I made this mistake with some old-crow tanks I painted and it makes the weathering and detailing stage much harder because your normal paints and inks don't like a rough surface.

So hopefully I have helped a bit! My main suggestion would be to buy a small selection of Vallejo model air as a test to see if you like them - you can use them neat and they do last a long time when you consider the coverage you get with an airbrush.

[papabees]

I had the same issue with alcohol so I just started using Liquitex Airbrush Medium. I will say I had the reverse experience of Robin in that I had to crank my pressure up much higher than I thought I would to get my brush to work properly. I usually spray at about 60psi and use a 50/50 medium/paint mix. That said, I do just use cheap acrylics so a higher quality paint could bring different results.

[ogre44]

I'll second the VallejoAir colors.
They're perfect right out of the bottle, and the thinner is great for thinning their other paints for use in an airbrush.
I just wish they'd make all of their colors available in the VallejoAir line, or at least have the decency to print up an equivalency chart

[kashirigi]

Part of the reason that I use Golden artist acrylics is that I'm a painter as well (on canvas, etc), so using it reduces the space and cost by half if I use it for modelling.

The Golden airbrush medium works very well, it's just that it takes a long time to dry. A mix with water and medium gives it a much shorter drying time.

As for drying mid-stream, the isopropanol is much more volatile than medium, so it would dry quicker (in the air). Even at high pressure, the paints thinned with Golden medium don't dry. Using that high a pressure causes other difficulties, though.

I'm starting to get a feel for what works, so that's something at least.

I may try out the Vallejo Air if I can find a local supplier. I find that Vallejo paints are overpriced, though, especially given the quality of Golden's paints and that I have some reasonable proficiency at mixing my own colours.

And as for mixing my own colours, I'm also not tremendously concerned about colour matching between models. If you've ever looked at any military vehicles, you're lucky if the paint on the vehicle is the same shade even on the vehicle. Plus they usually look like they were painted during a serious bender.

I was looking at an F-16 at a recent airshow, and it looked like it was painted by throwing buckets of paint at it, which it probably was.

[GJD]

Artist and modellers acrylics have a different formation in the medium that carries the pigment - artista acrylics are designed to thicker and slow drying , whereas model acrylics tend to be thiner and quicker drying, with a higher pigment density.

I use Tamiya acrylics and Revel and Tamiya colour mix. I mix roughly 2 parts paint to 1 part thinner using a bunch of cheap plastic pipettes, and get great results.

The one thing I would reccomend is picking up a moisture trap. The rapid flow of compressed air can lead to condensation forming. Most compressors have a moisture trap for the cylinder, but canned air really uffers badly and moisture can build up inside the air line if you spray for a while. Nothing worse than a great big blob of water spurting out and splattering all over your lovingly shaded miniature. The moisture trap sits between the airbush and the hose and catches the water before it gets spat out.

Nylon pipe cleaners are useful for cleaning too. Not woll or cotton, as they can shed and clog up the airbrush.

G.

[criticalmassgames]

Isopropanol should only be used to thin alcohol based paints such as Tamiya and Gunze Sangyo.

Tamiya do a gloss range (coded X) and a matt range (coded XF) the letter is followed by a number for the colour.

Gunze Sangyo paints go on slightly satin (and IMHO are the best paints I have for airbrushing). I find the colours from this range very rich.

Vallejo model air is water based (do not use iso here it will curdle the paint), is pre thinned and can go on straight out the bottle, but as a water based acrylic goes on slightly wetter than the Tamiya and Gunze Sangyo.

Life colour is another water based paint that can be airbrushed and only needs thinning a little with water (or their own thinner), this is perhaps the most extensive range of colour you will find for modelling.

[peabody]

I have airbrushed with Golden's airbrush line, Reaper Master Series, Tamiya, GW paints and Vallejo Model Air. About the only thing I haven't put through my airbrushes has been enamels.

I've come to learn that there are 3 'families' of paints and their respective thinners / driers:
1) Those that work well with an alcohol base such as Tamiya & Gunze.
2) Those that work well with an ammonia (glass-cleaner) base such as Reaper, GW and many craft paints.
3) Those that work well with an airbrush medium; effectively an acrylic medium designed to suit the demands of airbrush work. Vallejo Model Air and Golden Airbrush Colours are both good example of this.

So much of airbrushing is left up to hearsay, trial and error and myth. It can be discouraging and that's just not right because a double action airbrush with a good mix of paint at the right pressure is a joy and an inspiration to use.

Making an unfortunate thinner & paint combo can cost you a lot of time & frustration. It bugs me that this very basic and necessary information has to be cobbled together from all over the web. No wonder people often get tied into one brand, one type of paint and never explore beyond that. We all want and deserve predictable results with minimum fuss. Yet there are sooo many great colours just waiting to be sprayed...

I keep small squeeze bottles of water, Tamiya thinner, windex w/ Amonia-D and Vallejo airbrush thinner by my airbrush station so I can reduce any of my paints or acrylic artist's inks for airbrushing.

ALL AIRBRUSHING requires adequate ventilation. Amonia and isopropanol are both toxic. Wearing a dust mask is necessary, but does nothing for the fumes of these necessary thinners. Ventilation; fresh air, will mitigate your risk.

Not every paint is the same, so I NEVER mix in the airbrush cup itself unless I am 100% sure of the results. I use small disposable plastic condiment cups and mix what I need, paying attention to any reaction: coagulation or separation of my paint spells poor performance or an unplanned disassembly of the airbrush in the middle of a painting session.

Sometimes undiluted isopropanol (look at the percentage on the bottle!) or Windex can be too strong; that's when I use a little water to dilute them first before adding any paint or ink. This can be important when working with acrylic inks. A drop or two of water in the alcohol or glass-cleaner can mean the difference between curdled paint or ink and a smooth spraying vibrant colour. Add too much water and the resulting spray can take too long to dry, resulting in runs and a weak paint film that scratches easily.

Overly strong or concentrated thinner, whether alcohol or ammonia based, can also result in the nasty 'pebbling' or 'orange-peel' effect caused by paint drying before it hits its subject. This is why I recommend using the Tamiya thinner (glycol in the mix slows its drying time) and Windex with Ammonia-D; these are known quantities with reliable results.
Even if your goal is to save a lot of money over time, I suggest you still practice with the good stuff first to better understand what you should expect in terms of performance of home-mixed cheap thinners.

Not all airbrush acrylic mediums are the same. Golden's excellent airbrush thinner is not as suitable to our hobby as Vallejo's Model Air. The Golden thinner does not dry as fast or as hard, but it will thin their artists acrylics (thick or thin body) to an airbrushable consistency.

I always keep a piece of foamcore or cardboard that I have sprayed with primer on hand so I can test spray everything. This provides me the opportunity to adjust pressure, adjust consistency and tune for colour and transparency of my paint BEFORE I spray my models.

[kashirigi]

I think I do the same basic things you do; I also wear a NIOSH filter while painting for protection against organic vapours and use a spray booth.

My Grex airbrush warns specifically against using ammonia in the airbrush, so I haven't tried that route. My Badger 350 single action could probably spray rocks through it, but it's not designed to be the world's most precise airbrush.

Now that I've found out which paints are diluted with which solvent, my airbrush experience to date has been much more rewarding.

One thing I have not done is strain my paints through a nylon strainer. With the limited room I have and the potential for a horrible mess in a confined space, I have avoided this. So far it hasn't come back to bite me on the arse.

[peabody]

I am truly surprised that Grex warn against ammonia.... Wow.
I have heard nothing but good things about their airbrushes, and haven't hesitated to recommend them to folks just getting started.

But if we can't use Windex to thin paint and to clean the AB afterwards, that's not good news.

I know that my old Olympos and Iwata AB's have lost a good portion of their chrome factory finish inside the paint-cup over years of use due to a variety of cleaning products including ammonia based ones. Hasn't changed how they spray.
What else are we supposed to use to clean acrylics effectively? Ammonia based cleaners have been the standard for this for years.

[kashirigi]

Here's the verbatim warning:

Warning: Never use ammonia or ammonia based products on or in the airbrush. Ammonia will corrode the brass and chrome used to make your airbrush.

This is followed by a couple of sentences not to use abrasive cleansers

I imagine if you don't care about your finish, then it's A-OK, although I have no idea if ammonia is bad for the needle as it's made of steel.

[peabody]

Won't harm the needle, no problem there.