Airbrush clogging?

[Guest]

Hi guys and gals,

I've recently taken the plunge and bought an airbrush to try painting some of my models with, however I seem to have run into a snag. Whenever I spray with water I get a nice, smooth, continuous output. However when I start using paint, I get a short blast of coloured spray and then it stops. Sometimes if I wiggle the trigger back and forth I might get lucky and get another short blast, but then it stops again. I know it's not the air pressure because it's still kicking air out of the brush - it's just not blowing the paint out. When it does come out, it sprays evenly - there's no spattering or dribbling, or anything like that.

The compressor I'm using is an AS18K with a bottom-feed brush (the kit came with a gravity-fed brush as well, but no matter how much I thinned the paint, that one would not work at all!) and Humbrol acrylic paint thinned with water at a 2:1 ratio. I've even tried filtering the paint to try and get rid or any clumps prior to mixing! If I clean out the brush after this happens, again the water sprays nicely but on using paint it just starts all over again.

Could I have the brush set up wrong? Is it the paint? Is the brush just pants and needs replacing? Any advice or help would be much appreciated.

Cheers!

Paul

[Andy2035]

Hi Paul,

First of all, welcome to the forum...

May I ask what Airbrush your using, make - model and do you know what needle and tip size it has...

Is it all colours or just a certain one that blocks, do you pre-mix the paint before or do you mix it in the airbrush pot...

This also happens to me but only with certain colours and yes it is so annoying...

They're a great bunch in here so I pretty sure someone will know...

[Guest]

Thanks for the welcome Andy!

I don't actually know which make of AB I'm using, or the needle size, but it looks very close to the Badger which is featured in Lady_Phoenix's thread. Unfortunately it's one of those Chinese sets that comes with minimal instructions and appears to have been translated by Google!

As for the colours, I've tried it with several times with both Humbrol 27 (Sea Grey) and Humbrol 54 (Brass). Each time it's done the same thing. Ordinarily I'd prefer to use Revell paints, but I'm painting a kit which came with Humbrol paints so that's what I'm using. I've also tried mixing both in old paint pots that I've washed out, and in the airbrush pot itself. Again, seems to make no difference.

[Andy2035]

Are they Acrylic or Enamel paint's that your using...

[Guest]

Sorry, thought I mentioned before - they're acrylic paints.

[Andy2035]

Sorry, thought I mentioned before - they're acrylic paints.

You did sorry, I missed it...

[Guest]

Not to worry - the mind plays funny tricks at 04:00!!

Are there any types of paint that are more reliable for AB use than others?

[Guest]

Paz (hope that is right. Welcome to the forum.

Size of needle nozzle makes a great deal od difference. With my .4 size have not had any problem with Vallejo Acrylics at all.

But if I use a .2 size I have to thin by at least 33% sometimes more.

Look at the needle mine are marked with nicks at the end to indicate the needle size. Also ,even though water spurts thro, look down the nozzle against white paper & make sure the whole of the outlet is free.

Try more thinners the thinners marketed by the paint manufacturer. Water will thin down all the ingredients put in the paint to make it work as well as possible.

Last point what pressure are you working with on your compressor & does it have a water filter ?

Laurie

[stona]

I don't use those paints but agree with Laurie that thinning with the brand thinners is a good start. Later you might be able to revert to something different and add your own retardant (a product which will help prevent the acrylic paint drying at the nozzle/tip.)

You don't say at what pressure you are spraying. This is very dependent on the airbrush but most should spray acrylic paint in the 15-25 psi range. Have a play with the pressure regulater on your compressor.

Nozzles smaller than 0.3mm are not designed for spraying paints. They are designed for spraying inks,as used by graphic artists. Nothing is impossible but if your brush does have a small nozzle size spraying hobby paints will be an ongoing struggle. Even the best quality and very finest ground pigments,like for example in WEM's Colourcoats,may struggle in such fine nozzles.

Cheers

Steve

[John]

Is the brush just pants and needs replacing?

Sometimes it's a case of buy cheap buy twice, What PSI are you using on your compressor? you don't want it too high, if your looking for other paints try Model Air they are pre-thinned for airbrushes

Steve beat me to it

[Guest]

Nozzles smaller than 0.3mm are not designed for spraying paints. They are designed for spraying inks,as used by graphic artists. Nothing is impossible but if your brush does have a small nozzle size spraying hobby paints will be an ongoing struggle. Even the best quality and very finest ground pigments,like for example in WEM's Colourcoats,may struggle in such fine nozzles.

Cheers

Steve

Not heard that one before Steve but by accident & experience have latched onto that. Bought the .2 for smaller things such as those splodges on German aircraft. But had many frustrating troubles when I continued using the .2 thinking I was going to get a better finish. Recently have used the .4 & had no problems at all as said. I have also had a good look at the finish from both sizes & cannot see any difference at all.

One thing I did not mention. I started with a Badger & bottom feed and near gave up model making in frustration. The Badger is now not culled but a museum piece.

Regret as John has mentioned I ended up paying for two. But the difference was as the proverbial chalk & cheese. A top feed & as above at least to start with a .4 needle nozzle. Think you will find the majority will be using top feed as it just suits model making. Also with a good brush you can obtain spares for every different part & they are not prohibitive in cost.

It would not be me if I did not say try Vallejo Model Air. Not the only good acrylic paint by any means. But to start air brushing with, as I found, it is so easy to use. Comes ready for use in an airbrush BUT depending on what you are doing and with experience (using their thinners) thinning can enhance your work.

Hope with all this we have not given you info overload Paz but it is all from experience mine the recent 2 years, others, well they have long modelling beards.

Laurie

[BarryW]

Welcome Paul.

When I got back into modelling a year ago I started out using Humbrol acrylics and enamels but then switched to Vallejo Model Air and I found these much, much easier. I had a lot of problems with the Humbrols and would certainly recommend switching over. The eye dropped bottle in which Vallejo paints come in are also easier to use (but do get their own thinner).

As for nozzle size, I use 0.2 out of choice as I find the control easier than a 0.4 (which I tend to use for Gunze Mr Colour metallics). You do need to thin even Model Air down by about 50% for detail low pressure work and add a few drops of thinner for normal spray work. I also found my airbrushing also improved when I lashed out on a good airbrush, in my case a H&S Evo. I suspect that playing around and practising with the cheaper a/b and Humbrols actually helped make life easier when I did switch!!

I also recommend a gravity feed a/b - again I find them far easier to use.

If you want to learn about airbrushing there are some great tutorials on the Flory site. It does cost, about £3 pm but I consider it worth every penny. Here is a link.

- Home

Anyway - I hope that you sort your problems out, it can be a long and frustrating process getting used to airbrushing but it is worth it in the end.

[Guest]

Wow, lots of responses today! Thank you all for your input!

I actually have two airbrushes, which I've managed to find a little bit more about - the bottom-feed that I'm using, and the one described above, is an HS-28 with a 0.35mm nozzle diameter. The other one is a gravity-fed HS-30 with a 0.2mm-0.3mm nozzle diameter, which I've not been able to get to work with anything other than water despite watering one mixure down to a ratio of about 8:1! I had hoped to use this one because, as you said Barry, it feels easier to handle, but since it doesn't do anything....

I've looked at the needle on both of these brushes, Laurie, and neither has any markings on to suggest what size it is, and the nozzle is most definitely clear. I have noticed, however, that the very tip of the HS-30's needle is slightly bent at the very tip. That might be the problem with that one, maybe. As to thinners, I had a look on the Humbrol website and they specifically say that their acrylics should be thinned with water, not any special products.

My compressor has a max standby pressure of 53 PSI, and on constant feed maintains a steady 40 PSI, although after reading your advice, John and Steve, I've just adjusted it to run at 20 PSI . There are two water traps - one connected to the immediate output of the compressor, and a second one in-line between the end of the hose and the AB itself.

Something that I noticed when reading the previous airbrush threads before starting this one is that several people who have bought either this compressor or ones similar to it report that it runs very hot to the touch. Just thought I'd add that (so far, at least!) this has not been an issue for me.

Thanks again for all your advice everyone!

[Ian M]

You can thin humbrol and indeed other acrylics with water but use distilled water. Much kinder to the airbrush.

The only think with using water is that it weakens the paints. If Humbrol say other wise... They know better.

You can save the hooked needle with some very fine wet and dry. Just drag the needle to remove the hook then once that is gone, drag and twist at the same time to polish the tip evenly. As long as you are careful it will be ok.

Ian m

[stona]

A hooked or bent needle will definitely lead to blockages in the nozzle. Paint will accumulate in that bend,and in the case of acrylics,dry there. It can also force the needle off centre causing other problems. Try fixing the needle as per Ian's advice or replace it.

With properly thinned paint and a properly working airbrush you should be able to spray a thin pencil line with a 0.35mm nozzle. That's the size of my principle weapon (Iwata Eclipse). I also often use another brush with a 0.3 mm nozzle (because it has a much smaller paint cup) and honestly can't tell the diffrence!

Cheers

Steve