Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Been reading up but im getting conflicting opinions. The max psi i can get from my compresssor is 15, well it can do 35 for a 20th of a second withing a 1 and a bit seconds it holds firm at 15. I Read of people using higgh pressures to blast out vallejo polyurethane primers, as they were saying they dont like how the primer behaves when thinned so extra pressure needed. I've also read people saying they do thin it some with vallejo airbrush thinners some with just water. Really not sure which to trust. Now to pre-empt gear related questions, I'm using an iwata eclipse hp-cs, powered by a sparmax arism. I dont know if the primer colour matters or not, but it's the grey.

I've tried thinning it, nowhere nearly as much as for regular paint - probably as little as 10% of it being thinners.

The results were... disappointing. Yeah, disappointing is the best word. It tended to be thin and translucent on flat surfaces and pooled in recesses.

But, where's the harm in giving it a go on a test model?

I run it unthinned a 25-40psi. For varnish and primers I generally prefer a higher pressure and unthinned.

What I can tell you is if you run it thinnned you will need to use different settings and distances than unthinned.

yeah il give it a go on something that doesnt really matter so if i do a gak job it doesnt matter i thought my quite low pressure could become a problem in some cases. the guy at the store said he never really needed to run over 10 psi but hes not exactly going to be impartial.

il put a drop of flow improver in there to help it along, i guess this slightly thins paints but far less than proper thinner.

Don't thin the Polyurethane Primer.. Just my experience with it..
I only shake it up really well.. and spray it on with my airbrush..

Vallejo's website recommends not to thin it.
I shoot it unthinned, at 15-20 psi (I have a pretty bad compressor), and it works fine. I do have way more dry tips than with properly thinned paint, but nothing terrible.

Also, I used to put a coat just thick enough that I wouldn't see any grey plastic under the primer (I use the white PU primer), but now I spray a lot less. In color, I would say it's about half way between bare plastic and pure white. I've seen people recommend doing this, as it's supposedly sufficient to make the subsequent layers of paint adhere well to the mini, while reducing the loss of detail. I personally haven't seen much difference in drying time or durability (but I do let my mini dries for a few days after priming, and obviously I don't go out of my way to scratch the primer). Anyway, it might be worth looking into.

I usually thin it slightly, using a touch of Golden airbrush medium and a drop or two of water. Doesn't seem to affect the bond or surface finish, overmuch, and allows for spraying at a lower pressure with far less tip-dry. YMMV, as always.

Just an FYI on comparing pressure to other people on the interwebs, it's not always reliable, it depends on...

1. How accurate your regulator is (cheap hobby regulators are often off in their reading.

2. How much obstruction there is between the compressor (where pressure is measured) and the nozzle (where it actually matters). Longer hoses, extra filters, extra regulators, the design of the valve and how efficiently the AB gets air from the inlet hose to the air cap - all can be obstructions that require a higher setting at the compressor to get the same effective pressure where the air hits the paint.

So when someone says "I spray at X pressure", dont be surprised if that doesn't work for you.

Regarding vallejo primer, the stuff used to clog on me frequently so I thinned it a bit to stop the clogs, but in the end I didn't like Vallejo PU primer so swapped to a lacquer primer which I can thin to whatever degree I want and it still comes out good.

You're not supposed to thin their primer.