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Hi guys what would you recommend to use to water down Vallejo acrylic grey surface primer with an airbrush? distilled water or Windex?

Thanks.

You can thin Vallejo primers (and all water-based acrylics) with water, 1 part Flow Aid to 10 parts water, acrylic airbrush thinners (Testors, Vallejo, etc.), and very small amounts of isopropyl alcohol (Windex, but don't use the stuff with ammonia). Different thinners serve different purposes and will give the paint different properties. They can (and should) be used together.


Water - General thinning. Distilled water is often used because the process of converting water to steam and then condensing it back down again removes minerals that can build up over time in your airbrush. So long as you clean with distilled water, using tap water as a thinner is fine. If you live somewhere with fairly soft tap water, you probably won't even need to use distilled.

1 Part Flow Aid to 10 Parts Water - Flow Aid is a surfactant , meaning it breaks down surface tension (and therefore resistance to flow). This is my go-to thinner because it helps reduce tip-dry, which is a constant problem in a dry climate.

Acrylic Airbrush Thinners (Vallejo, Testors, etc.) - These are acrylic binders dissolved in water, meaning in practice they're paints that don't have pigments. If you over thin your paint with water, you'll notice the paint starts to pool in little blotches of color. This is because there's not enough acrylic binder to hold the paint together.

Windex (Isopropyl Alcohol) - You should be careful about using it as a thinner. Alcohol is carbon bonded to hydrogen, which is very different from oxygen bonded to hydrogen in the form of water. While I'll forgo the full chemistry lesson here,alcohol acts as a surfactant on steroids. If you have a bit of paint leftover in the cup after airbrushing, add rubbing alcohol to it a drop at a time and watch what happens. It's effective as a thinner in very small quantities (which is why people buy it pre-diluted in water in the form of Windex). Where it really shines is as a very effective and dirt cheap airbrush cleaner. Get the strongest you can find (i use 91%, but anything over 70% is fine) and dilute it yourself if needed.


When thinning paint, I usually start by adding equal amounts of water / flow aid mix and acrylic thinner. Then finish thinning with water. You'll also need to adjust over time for things like tip dry and the paint drying in the cup (or on the pallet) over time. How much of anything depends on the paint, color, and weather. With practice, you can read the paint and adjust accordingly.

It seems then that Distilled water is the easiest cheap option then for priming? I had issues with the primer being too easy to rub off with windex.

I've gone as far as 50% primer, 25% water, 25% flow aid when using Vajello Grey Surface Primer - probably overkill, but it went on just fine and sprayed nice and thin. You can dilute it a lot.

mechgrenadier wrote:
It seems then that Distilled water is the easiest cheap option then for priming? I had issues with the primer being too easy to rub off with windex.

Yes, but the primer rubbing off isn't usually due a problem with the solvent. It's more commonly because of impurities on the surface of the model or improper application. Vallejo primers are finicky in that they need to be applied in very thin coats that are allowed to dry fully or they don't work right.

Vallejo recommends not diluting their primer (http://www.acrylicosvallejo.com/en_US/model-paints/faqs/3 , section 7), and using a 0.35mm needle should do the trick.
I personally use a .5mm needle with no thinning, and don't have any issue. Just a little bit of dry tip after a while.

 Nodri wrote:

mechgrenadier wrote:
It seems then that Distilled water is the easiest cheap option then for priming? I had issues with the primer being too easy to rub off with windex.

Yes, but the primer rubbing off isn't usually due a problem with the solvent. It's more commonly because of impurities on the surface of the model or improper application. Vallejo primers are finicky in that they need to be applied in very thin coats that are allowed to dry fully or they don't work right.

It can be a problem with the solvent. Vallejo primers rubberise as they cure and I reckon Vallejo say to avoid certain thinners because they interfere with the process. They say on their website "It is recommended to avoid mixing Surface Primer with alcohol and/or solvents".

Personally I had nothing but trouble with my Vallejo primer regardless of how much I did or did not thin it. It did not spray nicely and was not as tough as I want a primer to be. I even tried going though 0.35, 0.5 and 0.7mm nozzles. So eventually gave up and moved on to other products. I was thinning it with their own brand thinner.


Automatically Appended Next Post:

 Nodri wrote:
You can thin Vallejo primers (and all water-based acrylics) with water, 1 part Flow Aid to 10 parts water, acrylic airbrush thinners (Testors, Vallejo, etc.), and very small amounts of isopropyl alcohol (Windex, but don't use the stuff with ammonia). Different thinners serve different purposes and will give the paint different properties. They can (and should) be used together.

I found when it comes to specific branded acrylic thinners they tend to be designed with specific paints in mind. For example, Humbrol Acrylic Thinner sucks with Vallejo paint because it has waaaaaaay too much drying retarder, but Humbrol Acrylics themselves dry way too fast and grains up when you airbrush it, so their thinner works well with their own paint to combat those features.

Likewise Gunze and Tamiya thinners are designed to work with alcohol based acrylics and I've found they don't work well with Vallejo's paints.

Never tried Testors thinner, you can't buy Testors acrylics easily in Australia.

I just use it neat, and it goes on fine

used it flat with no additives and it gave really good results, I am surprised at how thin it is already out of the bottle.