Thinning water based lacquer for airbrushing

[sihollies]

I have recently bought a small airbrush (0.5mm) and compressor with the ambition of acheiving a good streak free finish on my small projects.
I am completely new to airbrushing, and was wondering if anyone could could advise on how to determine the dilution ratio when using a water based lacquer.
I have some Mylands HB waterbased lacquer in stock, that I intend to experiment with.
On first attempt, I diluted it with 5% water, as I am sure I have read that this is the maximum recommended dilution ratio for water based finishes, but the airbrush just spluttered and failed to do much. I did up the pressure slightly, but it didnt do much. (May initial pressure was about 30psi).

Any advise would be massively appreciated .

Simon

 

[custard]

Nothing leaps out from that Simon, a 0.5mm needle should be good for a 1 1/2" or 2" spray pattern, there's no need to go higher than 30 psi, and 5% thinning is a good starting point.

Given the weather we've been having lately I'm wondering about the temperature where you're spraying? Viscocity and temperature are closely related, so if you're spraying in an unheated shed or garage it may well simply be too cold. Also drying times can become problematic as the temperature drops.

After that I'm afraid I'd be looking at "user error"! There are just so many little things that can go wrong with spraying, from your equipment to your technique, that I'd suggest cleaning everything down and checking all the basics step by step.

 

[sihollies]

Thanks for the reply
:-D
It certainly wouldn't surprise me if it is user error!
For info: I was in quite a warm environment,.
So if all the figures (dilution, pressure etc) look good to you, I will just experiment more.

Thanks again
simon

 

[custard]

Yes, I think practise and then more practise is the best plan. Just operating the button (especially with a two stage button) is a bit of a knack. A lot of people think water based spraying is easier than solvent based spraying, and in some ways that's true, but the thing with water based is that any solids that form won't redissolve the way they will with solvent based, so you need to be meticulously clean. That means your airbrush itself and maybe also straining the lacquer.

By the way, too warm is equally problematic to too cold! I doubt that's the problem here, but in higher temperatures you might need a retarder even with water based to stop orange pealing and deliver a smoother surface. You might step up the thinning a bit, but unlike with solvent based a little bit of water goes a long way, so I'd suggest something like 7.5% as a next step.

Good luck!

 

[Brandlin]

I use an airbrush a lot - but almost exclusively for paint (toy soldiers) rather than lacquer.

I can't comment on the dilution of 5% - in the world of paints the ratios are very different with a lot more water used to achieve a very low viscosity paint.

I agree with custard - you shouldn't need more than 30psi - in fact that may even be a little high depending on your equipment. If your brush is spluttering it would suggest either your paint/lacquer is too viscous or the particulates are too big, or more likely your brush needs cleaning.

Rule number 1 with an airbrush - more important the smaller your needle size - is ... it has to be scrupulously clean.

 

[sihollies]

Thanks for the replies.
The airbush is brand new, so cleanliness shouldnt be the problem.
I am using a dual action airbrush, as I was informed that it would be easier to use for a novice, such as I.

Would you say that there is a limit in regards to the percentage ratio of the thinning of the lacquer??

Again, any advice is appreciated, and I will keep you informed.

 

[Brandlin]

If you have run anything through the brush then dont consider it is new. It needs to be spotless.

A single action brush is simpler. But a dual action brush gives you a lot more control. Its arguable which is better to learn on. Changing from a single to a dual action means relearning, but you might find it slower to get good results with a dual action at first.... practice matters

When using the dual action make sure you always press down to release air before you pull back to introduce paint/lacquer. To start with keep your psi around the range you have it or perhaps a little lower and fully depress the trigger to introduce air, then practice introducing just a little lacquer and get used to the motions you need to create a smooth consistent flow. I would practice doing this just with water so that you can be sure how to get a result before you introduce the lacquer. That way you can be clear if its the lacquer or techniue that is causing the problem.

The general rule in airbrushes about consistency in paint in the modelling and art world is that it needs to flow like "skimmed milk". The pigment grain size is important... smaller is better, bigger can block the brush in an instant no matter how thinned it is.As i say my experience with lacuer is limited but i'm surprised by the 5% number. What you need to ensure is that you have a low viscosity medium with very small particulate size. Your 0.5mm needle size is relatively large so you should be less sensitive to viscosity chnages than a smaller needle.

 

[sihollies]

Many thanks.
For the moment, I am stuck with the dual action brush, so will persevere with that.
I have practised by running water through the brush and it seems to flow well, so am assuming that the 5% ratio for the Myland's lacquer is too concentrated??
Would you say that it may be detrimental to the final finish, should the lacquer be diluted more than the 5% recommended, or would it ust take longer to build the finish??

Many thanks in advance
Simon

 

[Brandlin]

I would dilute it until it is similar to skimmed milk. Then try some practice pieces. In the world i use my airbrush you would build up many thin coats. I dont know how your lacquer might react. Try it.

You wont regret a dual action brush - far better than single, but a greater learning curve is all.

 

[ED65]

I have practised by running water through the brush and it seems to flow well...

Spraying with plain water to test function is a good baseline test to do, good thinking; rules out the AB being clogged or a feed problem.

...so am assuming that the 5% ratio for the Myland's lacquer is too concentrated??

Yes far too much.

Simply put their suggested thinning ratio is just not suited to airbrushing. But I wouldn't be at all surprised to discover that it's not even sufficient for some sprayguns!

I've airbrushed for many years, similar to Brandlin, and the rule of thumb with all conventional airbrushes, with their tiny nozzles, is you thin a finish until it sprays well. Literally as much as it takes. And this usually means diluting past the point the manufacturer recommends, and sometimes way beyond what is suggested to be the maximum safe dilution.

Would you say that it may be detrimental to the final finish, should the lacquer be diluted more than the 5% recommended...

It might affect the way the finish works unfortunately, but you really have no choice. You have to try it and see.

I've never sprayed the Mylands stuff but I have successfully sprayed water-bourne finishes of every type imaginable all thinned to little more than cloudy water when necessary. So you can substantially thin water-bourne suspensions and still have them work despite what the makers tell us (and this is with paint, it works even better with clear finishes as a rule).

As a result I'm in complete agreement with Brandlin's suggestion above, aim for a viscosity similar to skimmed milk and see how that goes. My bet would be that it sprays fine (and possibly at a lower pressure too) and, very importantly, still dries properly.

Yes diluted this much you'll get a much slower build. But each coat may dry extraordinarily quickly, within minutes in warmer conditions. And if necessary you can use a hair dryer to speed up initial drying to 10-30 seconds, not dry enough for handling but enough that you can overcoat.

 

[ED65]

For the moment, I am stuck with the dual action brush, so will persevere with that.

On this bit Simon, yeah I don't think you need to immediately go out and get a simpler AB

I would suggest using this airbrush as though it were a single-action one though. So for now at least use it opened wide up to give good flow with a simple downwards press of the finger. This removes a variable, and opens up the nozzle (moves the needle back) which will substantially reduce the tendency to clog.

And about clogging, in case you haven't read a suitable warning yet clogging can be a real bugbear with airbrushes and water-bourne finishes are generally considered the worst for it. For periodic cleaning I would recommend having a small jar of suitable organic solvent, e.g. acetone, brush cleaner or cellulose thinners, whatever works well on the Mylands stuff, and a small brush on hand to dab or wipe the nozzle with (carefully!) before flushing through with clean water. It may be necessary to do this multiple times during a single spraying session of just half an hour or so to keep flow free and consistent.

 

[Droogs]

Hi sihollies,
As a starting point, you may find that a viscosity cup will help you get a mix you can use or at least a good starting point. ~they come in different sizes, go for the smallest you can find like a for 1 or 0 for the airbrush. hth

 

[AES]

Bit late on this one, sorry, (been fixing an annoying v slow water leak in cellar!) but maybe my own quite extensive experience of airbrushing (mainly for flying model aircraft - NOT woodwork) plus lately a bit of a mess about with a wooden toy tractor may help.

1st entirely agree with the others that for the sort of coverage you need you don't really need a double action AB, but now you've got it they really are the "best"(i.e. most potential capabilities), BUT you have to learn how to use it properly, and just as Brandlin has said, that takes PRACTICE. Then some more (practice)!
In fact I guess you could get by with only a single action/external mix brush (I use a Badger 350) for what you need but now you've got the double action brush (mine is a Badger 150) just stick with it because yours will definitely produce a finer line (and give you more "gradual graduations") than, say, my 350, even if fitted with the finest nozzle/needle. But (sorry again) it really does take practice - and to make matters worse, you'll find you need slightly different techniques and mixtures according to what type of paint you're using.
Did your AB come with a "Manual" complete with practice exercises? If not PM me and I'll send you a copy of what I got (years ago now) with my Badger 150. They really did help me to "get it" with air brushing.

2nd, also entirely agree with Brandlin that 100% cleanliness is absolutely VITAL, and sorry, but if you've used the AB once then it MUST be cleaned. You can get away with "flushing" the AB between colours during the same session (pure air + thinners and change the cup/bottle), but as soon as the session is finished then it's a complete strip, clean, and reassembly (careful with the needle)!

3rd Custard is dead right, temperature plays a big role when spraying (as does humidity, especially if spraying any sort of quick drying colour like cellulose). Personally I would not consider spraying any sort of paint or colour at all if the ambient temp in the shop is less than 10 deg C.

4th I think 30 psi is much too high and may be one possible reason why you're getting spatter (see item 5 below). Does your compressor allow you to adjust pressure? If so I SUGGEST about 15 to 20 psi should be enough. If not adjustable (like my Badger compressor)then get an extra long line to go between the compressor and the AB. Also, make sure to get the thick-walled type of line as both the thickness and the over-length line significantly reduce pressure pulses AND reduces output pressure at the AB itself, especially if there's no reservoir and pressure regulator on your compressor - probably not?

5th has your compressor got an oil/moisture trap between the compressor and the AB line? If not I highly recommend you fit one - this MAY be another reason why you're getting spatters (even if "only" using water-based paints/colours).

6th also highly agree with Droogs about getting a viscosity cup. If you're not familiar, this is basically a bit like a funnel with graduation/s (line/s) at the top and a certain size outlet at the bottom. To use, you mix up whatever paint and thinner then pour into the cup up to whatever line you choose (finger over the outlet) then open the outlet and time EXACTLY how long the mixture takes to pass through the cup. I doesn't matter which cup you use (I use a Ford, I think off hand it's a No. 7), but the point is you make notes of all the variables (different paint/colour type and brand, % mixture, quantity mixed, temperature) each time you use the AB so that you soon build up a "data base" of exactly what works for you under all conditions.

7th I'm not sure what medium you're using, but when I did the toy tractor I used artists acrylics for the first time (child safety and all that) and that stuff comes in a tube and is about as "fluid" as toothpaste)! I had to mix it down to 70+%, aiming, just as the others have said, for a consistency like milk (i.e. just a bit thicker than water - but NOT much thicker). To that I added a TINY drop of washing up fluid (syringe). You can use car windscreen washer additive instead. The idea of either of these is to reduce the surface tension of the mix when it's sitting in the AB bowl/cup

From what Custard has been saying above, it looks like your colour medium is a LOT thinner than the above acrylics I used to start with (!!), but using the "like milk" advice as a basic visual guide, that, added to the viscosity cup, will get you to where you need to be.

In short, the % mixture, along with an even slightly dirty AB (the orifices in double action brushes are REALLY tiny), line pressure, and water contamination are the other most likely reason/s why you were getting spatters on the job.

Sorry this is so long, but as the other posters have already indicated, it's a subject with a number of variables just hanging around to trip up the unwary.

HTH anyway.

With a double action AB you really do have the "best" tool possible (no matter what brand I think - it's what all the real airbrush artists use) and once you master it "the sky's the limit" as they say¨.

Good luck

AES

Oh yes, sorry. A quick P.S. Whatever medium you're using, a really thorough shaking/stirring before you start thinning for AB-ing is also absolutely vital. (In my model making days I used one of those battery-powered "joke-type" drinks mixer thingys. Really a joke those things, but VERY effective in making sure that no colour pigment was hiding at the bottom of the tin/jar).

 

[AES]

Another quick point I forgot, sorry. ED 65 is dead right about clogging, though he obviously has more experience of water base than my 1 or 2 goes so far (modelling, I used to use a lot of oil-based enamels thinned with cellulose, but that's a different subject!!!)

But he's dead right about having thinners standing by, even for a water-based colour, AND he's dead right about cleaning.

Look in the Chemists (Boots or somewhere in UK?) for those special tiny "bottle brushes" used for cleaning the gaps between your teeth. Choose the softest grade and the smallest possible diameter - these throw-away heads come in packs of 10 or so here. They just click into a little handle. Ideal for AB users.

AES

 

[Gerry]

A lot of modellers thin their water based paints using 50/50 screen wash/water mix.
The colour doesn't show in the finish and it helps flow and the prevention of blockages. It's the isopropyl alcohol that is the magic ingredient so you could try adding that to water at 10:1 (Water:IPA)

Gerry

 

[AES]

Personally I've never heard of using as much as that, I always "learnt" (from others) just a tiny drop. But why not, but I guess on what precisely your using for colour medium/paint, No?

AES

 

[Brandlin]

I broadly agree with AES. You don't need anything like that much additive.
I bought bottle of flow aid (which reduces surface tension and aids the flow of the medium through the brush) about 10 years ago, and i add maybe 2-3 drops to a 100ml bottle of distilled water that i use for thinning. I still have over half the bottle left.
If you were doing fine work i would recommend flow aid. If you are simply putting a lacquer coating on then i doubt you need it.

 

[sihollies]

Thankyou all for your wealth of knowledge and for sharing it.
A friend of mine persuaded me to buy the AB & compressor, as he stated the finish would be far superior than the brush technique I normally use, but he clearly didn't realise it isnt as straight forward as one might expect.
I like a challenge and think I have got one here!
I am sure the initial hiccups will be worth it in the long run, after I have grasped the technique.
The viscosity cup sounds like a 'must' for a beginner, so will certainly order one.

Again,
Thankyou all for your time
Simon