My airbrushing tale of woe

thinner and paint does not appear to be a good match, or one of them are getting a bit long in the tooth.

What's the thinned paint consistency? Is it milky? (with enamels it can be even thinner

Hi Grant,

It would be helpful to see a picture or two of the results that you are getting.

My first thought is that your paint is insufficiently thinned. I use a Sparmax SP-35C with Tamiya acrylics and I find that I get better results when the paint is mixed very thin. What model of airbrush are you using? I find that my SP-35C has a very linear progression to the paint flow and it does not generally go from a minimal flow to "full open" without a significant trigger movement.

I'm not quite sure what you mean when you say you're getting a "snow-like" appearance. Do you mean that you are getting a dusty/grainy finish which you can brush off with your fingers? If this is the case, you are most likely airbrushing from too great a distance and the paint is drying in the air before it reaches the surface of your model.

With Tamiya acrylics, I find I get the best results when the paint is very thin, air at low pressure (say around 15PSI)  and paint applied in multiple thin coats to build colour depth. Distance to subject in the range of 4-5 inches. I know you're using Humbrol enamels, but hopefully, this will at least get you into the game.

PS: Make sure that you are using a suitable paint thinner. Test-mix one drop of paint to one drop of thinner on something disposable. If the resultant mix is not smooth and contains lumps or strings, then it's not going to flow through the airbrush either. Humbrol should work ok with plain old mineral spirits and should mix to a smooth, uniform consistency.

Thanks for the response. The last test batch that I tried was a perfect mix of 1-part paint to 2-parts thinner. Other batches have ranged in ratio from  equal parts paint and thinner to 2-part paint to 3-part thinner.

The thiner is new and the paints have all been purchased in the last 3 months from the 2 biggest hobby shops in Perth so I would imagine there is a reasonably high turnover of stock.

I have heard about the "milky" consistency before and yes they do ressemble this consistency.

Your comment that the thinner may not be a good match for the paint is something that has been playing on my mind and one thing I failed to notice is that all of the paints that I have mixed with thinner are in glass bottles and if I let them stand for any amount of time all of the pigment settles in the bottom of the bottles. So for example the bottle of Interior Greent that I mixed for my Mustang P-51 has a large sedimentary layer of yellow in the bottom of it.

I must stress that all of this is new to me and I don't know if it is normal or not. I have not made models since I was a kid and did not have the money to buy paints so have no experience with them at all.

Thanks for the response

Grant

Hi Grant,

Thinned model paint does have a tendency to settle quickly (metallics more so) but it is not a problem - just stir it up again before putting it in the AB.  Just as an experiment,  try adding a little more thinner to your mix and see if it helps.

PS: I have tried the local "Diggers" brand white spirits (about $5.00 per litre at Bunnings) with Tamiya enamels and Testors enamels and both seem to work ok, so I would expect (but of course can't guarantee) that it should work with Humbrol as well.

Thanks Phil for your response, I have the same airbrush that you do.

Well I will keep experimenting with the mix although I am up to 1-part paint to 2-parts thinner already but I can try less no problems.

I see no evidence of lumps or string when I mix the paint with the thinner although when it sits in the bottles for a while I get a sediment of pigment at the bottom of the jar. I just shake up the bottle and stir before decanting some into the bowl of the airbrush.

Dusty/grainy is another way to describe the finish correct and I would have the subject matter further away than 4 to 5 inches so this sounds like the reason for the finish I am getting.

The paints definitely mix to a smooth even consistency with the thinner that I am using save for when they sit for while and a sediment forms in the bottom of the jar.

Cheers and thanks

Grant

Thanks Phil, I will keep experimenting with the mix and I will get some Diggers and try that as well. I can't remember the name of the enamel thinner that I am using but it was a generic brand that I bought from the local Paint Store in South Fremantle.

I can send some pics but it will be when I return to Perth next week as I am up in Port Hedland working currently.

Cheers

HangarHarry

Generic enamel thinner (I was told it is all the same);

What brand is the generic enamel thinner and what kind is it? It sounds to be the most likely source of the problem. Have you try a Humbrol thinner specifically formulated for their enamel?

Hi there and thanks for your response. I work 2000 kms from home and I won't be back home until next Wednesday. I will get you the information then. That sounds very vague I know but having been told it is all the same and that it doesn't matter I just bought and have not paid attention to the brand or type. I have not tried the Humbrol thinner specifically but the more I think about it the more I am starting to think it may well be the problem as well.

Put it this way, I have nothing to lose by trying the Humbrol and my even solve the problem. If the issue were the other way around and I was experiencing this problem with the Humbrol thinner then maybe it might be more of a concern.

I will give Humbrol a try when I get back to Perth and report my results.

Thanks

Phil_H

Hi Grant,

Thinned model paint does have a tendency to settle quickly (metallics more so) but it is not a problem - just stir it up again before putting it in the AB.  Just as an experiment,  try adding a little more thinner to your mix and see if it helps.

PS: I have tried the local "Diggers" brand white spirits (about $5.00 per litre at Bunnings) with Tamiya enamels and Testors enamels and both seem to work ok, so I would expect (but of course can't guarantee) that it should work with Humbrol as well.

All paints settle (I have about a dozen airbrush-thinned paints on the bench from the last build to prove it) - but how fast are these settling?

The closest paints to Humbrol that I use are Model Master enamels. They'll start to fall out of suspension within, oh, half an hour maybe. Noticeable separation by the following morning.

BUT...I've also used a certain other enamel that just would not stay in suspension. I'd mix it up, and by the time I could wipe off the stirring stick, the pigments were already dropping to the bottom of the cup. This was less than desirable and did an awesome job clogging up my Iwata airbrush.

So...I guess what's the time frame you're talking about for the settling? Is it a seconds, minutes, or hours issue?

Hi there and thanks for the information. I think my paints are falling out of suspension quite quickly although this is only intuition because I have not noted it explicity I have noticed that they are quick to form a sediment. The more I think about this issue and the more I read peoples' responses the more I suspect that the thinner is the issue.

I am going to purchase some Humbrol thinner and try that instead.

Grant

UPDATE

I purchased some Humbrol and Tamiya thinners and have today laid down some beautiful finishes to the surfaces of the parts for the 3 planes that I am building at the moment.

Interestingly it seems that the generic brand of thinners (which is Balchan Enamel Thinners) works fine on something like a Humbrol black (33 and 85) but mix it with primer, interior green, matt earth and it is just a disaster to use through an air gun although what I have already mixed with this thinner seems just fine for hand brushing so at least I haven't wasted my money on those pots of paint that I have mixed with it.

I want to say thanks to everyone who has contributed advice on this topic, it put my mind to rest quickly and has helped me solve the problem.

Thanks to you all

Grant