Problem with DIY airbrush thinner...

[Karnstein]

Back when I started airbrushing I used VMA paints+Vallejo AB thinner, then I managed to hunt up a local store that stocked the Liquitex AB medium and used it instead of the Vallejo thinner. Never had any real issues with those two in combination with VMA paints.

But that store closed down a while ago and after I depleted my stock, I decided to try out two recipes from other guys instead of simply ordering a bottle of Vallejo AB thinner.

Version a): 50% distilled water, 25% Liquitex Slow-Dri and 25% Flow Aid... that's the mixture Andrew from Schnauzerface uses. As far as I can remember I went with a bit more water (55%) and only 20% Flow-Aid.
Version b): 50% distilled water, 10% Matte Medium, 30% Slow-Dri and 10% Flow aid.... but I went with 25% SD and 15% F-aid

I skipped a bit on the flow aid in the first recipe, because the label on the Liquitex bottle recommends a 20:1 water:FA ratio and 25% of FA looked like a awful lot to me.

Earlier this week I tried both of DIY thinners with some colors from the Reaper Master Series through on some 28mm Norman kite shields. Instead of drying in a slightly prolonged period of time, the color coat turned out to be splotchy and took ages to dry.

<= took a picture halfway during my painting session... RMS templar blue thinned 1:1 or less with the DIY mix.

I then wiped off the still wet paint after a minute or two, cleaned my AB and tried again. Same paint, but thinned with a few drops of distilled water. This time I got a smooth and even coat, despite using the same thinning ratio, distance and pressure. No blotches, dried between the quick passes...

My guess would be that the additive ratio is too high, but I'm not 100% sure if it is something that can be fixed. The next things I want to try is a) thinning down a portion of the already mixed paints 1:1 with more distilled water and b) mix some distilled water with the flow-aid according to the label on the bottle (20:1 parts) and then use that mixture with 25% Drying retarder. Since the label on that bottle says "don't add more than 25% to the volume", it shouldn't breach the producers recommendations as long as I don't thin down my paint too much.

Has anyone suffered similar mishaps and if you did, what was your solution?

 

[QuietiManes]

Don't add more than %25 means when you're adding %25 you are pushing your luck. Calm down on the retarder if you want it to dry. You know it, let yourself do it. Lol. You also may not know that most paints have additives in their mix. So, reducing the additives by a fair amount is a good idea to start with.

That "home made reducer" is only required when you start needing it...when your paint starts drying too fast you start adding in a bit of the retarder (not starting with the max amount on the bottle)...when your paint isn't atomizing right, isn't laying on smooth, you start adding a BIT of the flow aid...etc. Water will probably suit you fine, without any additives. 20:1 is %5.

 

[jabbayoda]

I usually recommend 50% distilled water, 40% drying retarder, and 10% flow aid. I try not to go too heavy on the flow aid, as a little bit goes a long way. The drying retarder works well to avoid tip dry, so I like to throw a lot of it in there.

 

[Einion]

Back when I started airbrushing I used VMA paints+Vallejo AB thinner, then I managed to hunt up a local store that stocked the Liquitex AB medium and used it instead of the Vallejo thinner. Never had any real issues with those two in combination with VMA paints.

In case you don't know, airbrush mediums are designed to be used in any amount. From this we know that they're not merely water + ingredients to improve flow and slow drying; they must include some binder. So if that's the thinning agent you're used to I'd recommend you work towards replicating it, assuming you don't want to go with water.

I skipped a bit on the flow aid in the first recipe, because the label on the Liquitex bottle recommends a 20:1 water:FA ratio and 25% of FA looked like a awful lot to me.

I'll say! (See next point.)

Earlier this week I tried both of DIY thinners with some colors from the Reaper Master Series through on some 28mm Norman kite shields. Instead of drying in a slightly prolonged period of time, the color coat turned out to be splotchy and took ages to dry.

Just from looking at the pic it looks like you're spraying from too close to me, if you'd misted that same paint on I'd have bet the results would have been better. But the very slow drying would indicate that there's too much of something (or somethings) that are retarding drying as you suspect.

Since any amount of Slow-Dri Blending Medium can also be added if that's the exact one you're using it's the Flow-Aid alone that's the issue. If you're using Slow Dri Fluid Retarder it's both.

Flow-Aid is recommended to be added at maybe 5% maximum, in relation to the total paint volume.

The next things I want to try is a) thinning down a portion of the already mixed paints 1:1 with more distilled water and b) mix some distilled water with the flow-aid according to the label on the bottle (20:1 parts) and then use that mixture with 25% Drying retarder. Since the label on that bottle says "don't add more than 25% to the volume", it shouldn't breach the producers recommendations as long as I don't thin down my paint too much.

That's 25% in relation to straight paint, not 25% in addition to paint mixed with other additives, and that might have to include water too - so only 20% retarder, 60% paint and the rest water might actually result in too high a proportion of retarder.

General rule of thumb with retarders is to add the least amount that gives you a beneficial result, definitely not the most you can get away with

This bit last:

I then wiped off the still wet paint after a minute or two, cleaned my AB and tried again. Same paint, but thinned with a few drops of distilled water. This time I got a smooth and even coat, despite using the same thinning ratio, distance and pressure. No blotches, dried between the quick passes...

Perfect example of why I consistently recommend trying just water to begin with Given the success here, is there a reason you don't want to continue to thin with water alone?

Einion

 

[PegaZus]

Perfect example of why I consistently recommend trying just water to begin with Given the success here, is there a reason you don't want to continue to thin with water alone?

Einion

Seconding Einion's point. Bought an airbrush this last summer, partly so I'd have it and partly to paint some model car bodies the kids and I were doing. Got the notion of using Windex as a thinner. Was really disappointed in the results and what I was getting looked just like your image. So gave up and tried straight water with the cheap craft paints we were using.

Straight water worked like a charm.

 

[Karnstein]

Since any amount of Slow-Dri Blending Medium can also be added if that's the exact one you're using it's the Flow-Aid alone that's the issue. If you're using Slow Dri Fluid Retarder it's both.

Flow-Aid is recommended to be added at maybe 5% maximum, in relation to the total paint volume.

I used the retarder from Liquitex, not the blending medium...

That's 25% in relation to straight paint, not 25% in addition to paint mixed with other additives, and that might have to include water too - so only 20% retarder, 60% paint and the rest water might actually result in too high a proportion of retarder.

General rule of thumb with retarders is to add the least amount that gives you a beneficial result, definitely not the most you can get away with

*scratches his head* Yeah, sure I think I get it. If I already hit the 25% mark when I'm just thinning my paint 1:1, I risk overdoing the retarder by accident.

But let me see if I can muddle through somehow...

I used a 60ml bottle for both mixes. The first one was made up by 35ml of water, 15ml Retarder and 10ml of Flow-Aid (which is six times the recommended ratio). I already transferred the mix into a 80ml bottle, adding 20ml of distilled water. That leaves me with a 18% FA ratio (55W:10FA) and less than 20% of my mix is made up by slow-dry. If I mix that one 1:1 with paint I'm relatively fine in regard to the SD, but it gets wonky if I go for a higher thinner/paint ratio and I'm way beyond the recommended FA limit anyway. To achieve a proper water:FA ratio, I would need to increase the amount of distilled water from 55 to 200ml (5% of that =10ml FA initially added). In which case I would end up solution that contains 7% Slow Dry.

The second recipe should be easier to fix. I started with 30ml water and 5ml Flow Aid. The right ratio of water for 5ml of FA would be 100ml of water, so I only need to add 70ml of water and the ratio is fine...If I go for a more cautious approach and grap a 150ml bottle, I would end up with with a 24:1 water to FA ratio and a 13,33% of the mixture would be made up by Slow-Dry (20 out of 150ml).

Am I right or did I lost my math skills somewhere in the past...