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Measuring paints and thinners and achieving ratios


Filler

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I have always struggled with paint thinning and mixing. I’ve never been able to get my head around the “like semi skimmed milk” description and even 50/50 mixes are a problem, especially with very small amounts of paint. The way paint v thinner drops out of a cheap pipette just seems different.

 

Anyway, I was wondering what people’s approaches are and if anyone uses those pocket scales that claim to measure to 0.01g. And how different is the density and weight of lacquer paint and thinner?

 

Or am I way overthinking this and just ‘roughly’ 50/50 is good enough?

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Never have I ever. 

My eye is the first measuring tool. The way the mix moves in the cup, how "liquid" it is. 

Second measuring tool is my ear. If you hear the airbrush crackling something's up. Typically during summer thinner will evaporate faster (I use 99% lacquers) so the mix will actually become thicker...when it happens I hear the airbrush starting to sound differently and I feel the need to up air pressure. I just add a drop or two of thinner in the cup and remix and it's all good again.

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So, a bit like Star Wars where Obi Won Kenobi tells Luke to 'use the force' and he turns his electronic targeting thingy off. I expect that is probably the most common way then. I guess I just need to paint more and get the experience where I can 'feel' what is right.

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I find a good mix ratio varies from brand to brand and even with different paints of the same brand. My method is to mix in a glass jar, adding thinner until it achieves a consistency where a drop of paint will run easily down the side of the glass but leave a translucent mark of colour behind. Hard to explain in precise terms, but with a bit of trial and error, you'll find the right level. Once you know it for one paint you have a visual reference for all paints and you can forget about working out ratios.

 

I use enamels and solvent based acrylics. I've not tried it on water based acrylics.

 

Cheers

 

Colin

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Some good advice right here. Like our colleagues have said, the more you paint, easier it will get. I would suggest getting a few cheap kits and using them to experiment with paint. You can also experiment on plaatic card stock, but I have found that it's actually better to use real kits. Firstly, clean the assembled kit with some IPA (not the beer :)), and spray away. Also, for the thinning, get some revell mixing cups, or similar. Revell cups come with markings on the side so it's pretty easy to mix exact quantities, and get repeatable results. This should get you started and spraying in no time.

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Thanks for the advice everyone. I'll give the scales a miss and just learn to do it consistently by eye. I do use cheap disposable pipettes, but I feel that half the paint remains stuck to the pipette whereas the thinner largely transfers to the mixing dish. It's when preparing very small amounts of paint for say just spraying a seat or a pitot or something. No point thinning 10ml to do that.

 

 

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56 minutes ago, Filler said:

It's when preparing very small amounts of paint for say just spraying a seat or a pitot or something. No point thinning 10ml to do that.

I usually prepare paint in 10 ml batches and store it in recycled tamiya type bottles, so I always have some ready to go. I've found the thinned stuff (enamel or spirit based lacquers) keeps pretty well as long as the bottle is around 1/3rd full or better. Over time you'll build up a range of pre-thinned paints ready to go - ideal for the situation you describe. Just make sure the container is truly air tight. I used to use the spare tins you can get from Hannants, but found the sealing a bit hit and miss.

 

Cheers

 

Colin

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Some years ago, while at the grocery store just up the street, I bought a pack of a half dozen glass eye droppers. Recently, while either at the same store or the nearby pharmacy, I saw a similar pack of droppers. They work great with paint and are easy to clean.

 

51910415586_a7e9f10ce5_b.jpg

 

 

 

Chris

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You're definitely overthinking this. You don't need anything like that level of precision.

 

What you do need is a good starting point for the paint and thinner you're going to use and how you're going to apply it (paint brush, or airbrush with needle size 0.something mm) which someone else is already familiar with. Once you see what the consistency is supposed to look and feel like you just need to get your paint approximately like that in future for fairly consistent results.

 

It's more art than science really - because different colours can and do have different viscosities in the same brand of paint. Hence a precise thinning ratio for one colour might not be quite right for another.

 

It's better to do it subjectively but I acknowledge you first need to know what good looks like.

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4 hours ago, Filler said:

but I feel that half the paint remains stuck to the pipette whereas the thinner largely transfers to the mixing dish. 

 

For this reason I first pipette the thinner into the mixing cup, then suck in the right amount of paint. I then suck the paint and thinner mix in and out of the pipette. Not only does it mix them pretty well, it also washes out more of the paint.

 

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8 hours ago, Filler said:

So, a bit like Star Wars where Obi Won Kenobi tells Luke to 'use the force' and he turns his electronic targeting thingy off. I expect that is probably the most common way then. I guess I just need to paint more and get the experience where I can 'feel' what is right.

Have you not seen Tamiya's Extra Thin Midi-Chlorians Thinner? Standard square bottle but the lid can be Light or Dark.

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  • 1 month later...
On 1/10/2023 at 11:35 AM, Filler said:

I’ve never been able to get my head around the “like semi skimmed milk” description and even 50/50 mixes are a problem

I had a similar experience before I moved to a better airbrush and compressor. 

Then I realized "oh that's how they get away with such thin paint, their airbrush doesn't hose down the part with a torrent of paint"

 

 

 

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I do it by eye, measurement is so restrictive.

 

There are so many variables both in paint, thinner as well as existential variable like temperature and humidity. Then of course there is the airbrush to consider and what it likes and what air pressure and volume settings.

 

After mixing I judge by eye as to how it runs down the side of the mixing cup when squeezed form the brush on the edge of the cup.

 

As in all of this game practice makes perfect.

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There’s definitely an art to it, and the very experienced modelers here have learned through experience to mix by eye. There are also some people who take a scientific approach, such as Dr. Strangebrush who is a trained chemist. His store is on the wrong side of the pond from you but perhaps you can take a look at some of the measuring vials and beakers he offers to get some ideas. He also offers some extensive information on mixing and airbrushing, and regularly appears on podcasts. 
 

https://modelpaintsol.com/model-painting/bottles/page/2

 

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  • 3 weeks later...

I think one of the challenges with trying to be scientific about it, for the average consumer at least, is that all we can really measure at home is volume (or mass, at a push) whereas what we want to directly control with thinning is the viscosity. Even sticking to a single brand and single product line, different discreet paints within it will have some degree of variation in viscosity as whilst the binder remains the same, the presence (or absence) of flatting agent will thicken the paint (or not) and even commercial colourants change viscosity quite drastically at different temperatures and of course all at different rates. For ours for instance, a paint with a lot of white and/or iron oxide yellow (an ochre sort of colour) content will be thicker at any given temperature than a paint with very little of those in it, assuming total pigment content is equal per colour (which isn't a given).

 

It's good to have a starting point though to help people get into the right ballpark, but overall that's why it's generally done by look and feel through practise rather than measurements. One definitely could do it by measurement, but the exact ratio of thinners to paint will vary from one colour to the next. It won't double or half from one to the next, but it will vary enough that careful measurement isn't necessarily going to give the desired results.

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58 minutes ago, Jamie @ Sovereign Hobbies said:

I think one of the challenges with trying to be scientific about it, for the average consumer at least, is that all we can really measure at home is volume (or mass, at a push) whereas what we want to directly control with thinning is the viscosity. Even sticking to a single brand and single product line, different discreet paints within it will have some degree of variation in viscosity as whilst the binder remains the same, the presence (or absence) of flatting agent will thicken the paint (or not) and even commercial colourants change viscosity quite drastically at different temperatures and of course all at different rates. For ours for instance, a paint with a lot of white and/or iron oxide yellow (an ochre sort of colour) content will be thicker at any given temperature than a paint with very little of those in it, assuming total pigment content is equal per colour (which isn't a given).

 

It's good to have a starting point though to help people get into the right ballpark, but overall that's why it's generally done by look and feel through practise rather than measurements. One definitely could do it by measurement, but the exact ratio of thinners to paint will vary from one colour to the next. It won't double or half from one to the next, but it will vary enough that careful measurement isn't necessarily going to give the desired results.



 

However there are exceptions. For example, Mission Models paints typically airbrush fine at a higher viscosity than other acrylics. They rely on a poly additive that’s added with thinner to make their thicker paint flow.
 

And I’ve experienced say…clear coats from different manufacturers with the same apparent viscosity - one will clog, one won’t. 

Edited by CFster
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