paint issues

Tamiya acrylics are alcohol-based and should never be thinned with water.

I have never had a probluem with Tamyia paint but like everyone else here don't use any thinner other than the paint manufacturer's brand I learned that a long time ago.             ACESES5                      

RO water and alcohol?  Never heard of using a mixture like that to thin paint. If you're using Tamiya acrylics, use Tamiya's brand of airbrush thinner. Don't mess around with using weird mixture for thinning paint for airbrushing (alcohol and RO water)

I would first start with cleaning your airbrush to remove any dried up/caked on paint residues. I hear lacquer thinner does the trick to remove stubborn dried paint.

The only paint that can be used straight from a bottle is Vallejo Model Air brand. All others have to be thinned.

Situations like this is why I now suggest to newbies that they buy only brand name airbrushes and to use the thinner brand that goes with the paint brand. Even when the paint brand says you "can" use a certain generic not all generics are the same. This isn't a guaranty of no problems but it does reduce them. There is always a chance of getting a bad/old batch of anything.

In my opinion the difference in cost is negligible especially if you factor in wasted materials and time in solving a problem.

All of the above doesn't apply to those with extensive experience who have learned how to "make things work".

That bottle of X-20 lasts forever,I use a dropper to to measure it out.

i double checked and it was set to about 35-40 psi, so i cranked it down, also i looked up how much thinner people use, and it seams most people do between 30-75% thinner. so ill go pick up another bottle and try again

Sounds like a case of the paint drying before it reaches the surface, in effect it's like blowing dust all over the model.

How much air pressure are you using and how far from the model are you spraying? If you're above about 18PSI, you're using too much air. If you're able to pump unthinned Tamiya acrylic through your brush, you're using way too much air.

Drop the pressure and get up close and personal. If your paint is running or spidering when you do that, then back off on the trigger and reduce the paint flow. You're using double-action brushes. 

Though it works to an extent, don't thin Tamiya with water. It increases surface tension, induces separation in the paint and reduces adhesion. Thinning flat Tamiya acrylics with water can often result in a chalky, spotty finish, even if everything else is optimal. 

Straight Iso works to an extent, but in hot, dry conditions it can contribute to the problem you're having. Tamiya's X-20A thinner incorporates a retarder to slow the drying of the paint and may help reduce this.

ive seen many many people use all sorts, most using the brand thinner, the alcahol, or water. but ive seen many people use window washer fluid. i also double checked my pressure and it was about 35 psi so i dialed it down to about 15

tetraodon

ive used isopryl alcahol and regular RO water.

I've only used Tamiya X20 thinner. I suppose I'll be quiet and let folk with more experience with thinning Tamiya with other than their own thinner.

I asked on the off-chance that you were thinning with something strange, but you're not.

ive used isopryl alcahol and regular RO water.

May I ask what you used to thin it? Tamiya sprays like a dream, normally.

i cant get a good enough pic to post, i use a badger 155 anthem and a masters double action, the paint was horrible though both brushes,

It's all about practice,you need to experiment until you get the right consistency and the proper pressure.Tamiya usually performs well and is a user friendly paint.I have a Badger 150,for basecoat,I eyeball the mix to the consistency of skim milk and shoot at 15-20 psi, 5"-6" If i'm doing camo close in,I dial the pressure down to 10-12 psi and thin it out more.

But again,it's practice-practice-practice  no tricks or magic formulas

It would also be helpful to know what kind of airbrush,double or single action ?

I've never had a bad Tamiya acrylic paint.  Based on your description, it's hard to tell what happened.  Why don't you post a pic?