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Hi, guys. I am using an Iwata Neo airbrush with 2 moisture traps and a mastercraft compressor, trying to spray Vallejo Grey primer. the results end up slightly grainy and I am wondering how I can fix that? its pretty humid but I am doing this in a closed garage with two traps.

Vallejo primer is pretty awful to airbrush with, you can't use it straight from the pot or it clogs too easily, you need to thin it AND add a fair bit of flow improver to it and even properly applied it has poor adhesion. Pick up some Badger Stynylrez primer, it's much better

I have some coincidentally in white but the same problem occured. slightly grainy texture when ran straight through, I shook the hell out of it too.

A little bit of flow improver solves pretty much everything for me (a bit more dry tipping than with normal paints, but it goes on very smoothly).
I use a pretty high pressure, and a .5mm needle (although it also works fine with a .3).

If it's coming out grainy in texture, you're spraying from too far away. Maximum distance with an airbrush shouldn't be more than 6".

Okay I ordered some vallejo flow improver to try it out. I use high pressure as well so that may be it.

mechgrenadier wrote:
Okay I ordered some vallejo flow improver to try it out. I use high pressure as well so that may be it.

When painting minis you shouldn't be running higher than 20psi.

I've primed hundreds of infantry and vehicles with Vallejo primer without any problems, so I think there must be a major difference in how we apply the primer to the model.

I use a 0,4mm needle/nozzle set at 60 PSI when priming or applying clear coats and use the primer straight out of the bottle, without any additives.

I aim for a moist consistency of the primer on the model - since the primer is self-leveling. If your primer is grainy on the model, it has partially dried before it hit the model, so I'd look at spraying distance and temperature and adjust accordingly.

 Ghool wrote:
When painting minis you shouldn't be running higher than 20psi.

 Stephanius wrote:
I've primed hundreds of infantry and vehicles with Vallejo primer without any problems, so I think there must be a major difference in how we apply the primer to the model.

I use a 0,4mm needle/nozzle set at 60 PSI when priming or applying clear coats and use the primer straight out of the bottle, without any additives.

Now there's some difference in usage!

tneva82 wrote:

 Ghool wrote:
When painting minis you shouldn't be running higher than 20psi.

 Stephanius wrote:
I've primed hundreds of infantry and vehicles with Vallejo primer without any problems, so I think there must be a major difference in how we apply the primer to the model.

I use a 0,4mm needle/nozzle set at 60 PSI when priming or applying clear coats and use the primer straight out of the bottle, without any additives.

Now there's some difference in usage!

Not really, painting isn't priming.
When painting, acrylic paints on minis most people use low pressure. Since pressure and nozzle dictacte working speed, i.e. how far long you can spray an area before it is flooded, in the interest of control low pressure is a very good idea.

However, when priming a model or a vehicle, I'm perfectly fine with a fast working speed, since I'm trying to cover the entire model in one neat layer of primer.
Higher pressure in combination with a bigger nozzle helps with higher viscosity materials such as primer, clear coat or Tamiya alcohol paints by mitigating the chances for clogging.