I use syringes to achieve exact ratios when preparing paints for airbrushing. However, it's difficult for me to achieve the thinner-to-paint ratio of 95 to 5 when creating an oil filter because it's difficult to measure the volume of a drop of an oil paint. Do you simply eyeball? Or, do you use a certain method?

Chrisk,

19.2 parts thinner to 1 part paint or simply,

20 parts thinner to 1 part paint.

Cheers,
Joe

. Okay let's split hairs . If you want accuracy why not not just weigh the mixture . How about one of those little electronic scales ?

Of course, I know that. It's easy to measure the volume of thinner with a syringe or an eye dropper, but it's not easy to measure the volume/weight of a drop of an oil paint.

Let's say I want to create an oil filter with a paintball sized oil paint. How much thinner should I add? OK. My guesstimate is the volume of a paintball sized oil paint is about 0.1 ml. So, I'll add about 2 ml of a thinner.

Edit: Oops... I misread your post.

I thought you were trying to create a filter that looked like oil, not that you were trying to use artist oil paint as the color part of the mix.

The viscosity of the artist oil paint is much greater than your thinners, so I'm not sure that a precise mixing ratio is even valid. I think the best you could do is to just estimate a portion of the oil paint that looks to be the same volume (approximate size and shape) as a single drop of thinners.

Be sure to be consistent in where you scoop the artist oil paint "blob" from. Artist oil paint tends to separate slightly in the tube and sometimes you get more oil and sometimes less which would effect the volume of pigment.

I would simply take a toothpick and scoop up a small "blob" of the artist oil paint that "looks" about right. The measuring ratios are explained below. Since you can't measure out a half-drop of thinners to make 9 and 1/2 drops, you still can't use a total mixture of less than 20 total drops (19 thinner and 1 paint).

Anyways...

Original answer:

Chrisk,

Go to the nearest Walmart to the pharmacy section and get some of their "medicine droppers" (eye droppers). Walmart has them in a carded two-pack with glass tubes and removable rubber bulbs.

They're cheap and easy to clean. Just pull the bulb off and wipe out the glass tube with a twist of paper towel moistened with a thinner appropriate to the type of paint. They're cheap enough that you can throw them away if they get too dirty to clean or you break the glass tube. I usually wear out the rubber bulbs first, though, because they're so easy to keep clean.

(You can probably get similar medicine droppers at any pharmacy like CVS or Walgreens. I've just been buying mine from Wally World so long I don't even look anywhere else.)

Custom mixes are quite simple using a single drop as the smallest measure possible. This gives 10 drops as an easily reducible 100%.

For your 95:5 ratio just reason the math out.

A 90:10 ratio would be 9 drops of thinner to one drop of paint for a total of 10 drops. 10% is twice 5%, but we can't measure out 1/2 of the single drop which equals 10% in a 10 drop mixture, so we double the 10 drop total to 20. That is, 10% now equals 2 drops. One half of that is one drop for 5%.

This then gives us 19 drops of thinner to one drop of paint, or 95:5.

Ratios that are already reduced to something that will divide into 10 can be measured out in quantities of less than 20 total drops.

For instance, I'm using a custom paint mix right now on a project that's 3 parts of one color and 2 parts of another (60:40). Easy peasy... that's 5 drops total (3 drops of one plus 2 drops of the other) plus whatever I need to reduce the paint to spray.

Be sure to write down your custom mixes for later and you can always reproduce exactly a color you've used before.

One more tip:

Always rinse the eye-dropper out before measuring out the next color of paint (not necessary with thinners), since the paint still in the eye-dropper will throw off your color mixes. This is very important when your total mixtures are in the 20 drops or less volume. The single drop of paint left in the eye-dropper will effect the result.

After adding the last drop of the last color and thinners to the mix, rinse the eye-dropper and then use it to actually mix the paint by sucking the paint into and out of the eye-dropper. This makes for very thorough mixing.

Might sound like a lot of work, but after you get used to mixing paints using drops as your base measurement, the math will become second nature and very fast to figure out.

HTH,

The reason why I'm concerned with the ratio is if an oil filter is not thinned enough, it'll take a long long time to dry. Conversely, if it's way too thin, it will hardly have any effect.

I have a love-hate relationship with oil paints on models. They make models look great but take too long to dry. I now use MIG oil paints which supposedly dry faster than artist oil paints. However, it still takes days for MIG oils to dry. Since oil paints dry by oxidation, I cannot accelerate dry time by placing the model in my home-made paint dry station.