Brush Painting Tamiya Acrylics

[FlyingSnowmew]

What ratio should I use of Tamiya thinner or 91% isopropanol to thin Tamiya acrylics in order to brush paint them over large surfaces?

How much gel retarder should I add?

How many coats should it take for full coverage?

[Bigasshammm]

What ratio should I use of Tamiya thinner or 91% isopropanol to thin Tamiya acrylics in order to brush paint them over large surfaces?

How much gel retarder should I add?

How many coats should it take for full coverage?

Good luck I'd like to know this answer too. I've never enjoyed brush painting even the smallest things with Tamiya paints.

[Triarius]

The amount of thinner depends on the conditions and the area you need to cover. At 50-60% relative humidity and 68-70° F, I'd start with 5 to 10% by volume, maybe increasing that to 10%, but I wouldn't go any higher.

The amount of retarder I generally use is about half a drop (from the Golden bottle) per 60 ml. of solvent (I keep a bottle of stock solution on hand.) You can double that amount, but no more than that. Also, be sure to completely dissolve the retarder in the alcohol before adding it to the paint.

With acrylics generally, and Tamiya and Gunze in particular, you don't so much as brush it on as flow it on from the brush, painting with a wet edge. This will result in a relatively thick coat, but it will shrink right down on the surface. Three times NEVER try to go over an area already painted until initial set (tack free) of the paint. This means that with darker colors, at least two coats, waiting 24 hours between coats. With problematic colors, like white and yellow, at least three coats. Undercoating white with silver, or yellow with silver or white will help. Also undercoat bright reds with white or silver.

If you are unfamiliar with brushing Tamiya acrylics, I strongly recommend practicing first until you get the hang of it. It's much more of an art than a science. I have little trouble with them (most of the time ), but I'm a paint geek, with vastly more experience at paint wrangling than most modelers. :P

[Old Blind Dog]

I hand brush Tamiya acrylics quite a bit and have no difficulty. I use Tamiya's own X-20 A thinner.

1. Decant some paint from the bottle into a separate pallet.

2. Add X-20 A thinner drop by drop from a pipette until the paint is at the consistency of skim milk.

3. Put some X-20 A into a small separate pallet such as a bottle cap.

4. Dip brush (soft sable) into thinner

5. Dip brush into paint

6. Wipe off excess paint on the clean edge of a third pallet (never on the paint jar itself)

7. Apply paint in light even strokes Never go over the same area more than once per coat.

8. Always brush in the same direction coat after coat.

9. Repeat as needed.

cheers

Old Blind Dog

[Triarius]

Old Blind Dog's detailed instructions are just about perfect, IMHO, although I think his thinning ratio is a bit high—but "the consistency of skim milk" is not a precise term (nor should it be) and is perceived differently by different eyeballs (and the gooey gray stuff behind them.) Thanks for filling in everything I left out! Odd how the brain filters out details of something has become a familiar routine:

"How do you do that?"

"Oh, I dunno, it's just routine…"

Yah. Right. Like riding a bicycle—and the experts have the scars on their knees to prove it.

BTW: Tamiya's X-20 A contains a retarder, so don't add any more to it. X-20A is essentially 90+% isopropyl alcohol with a retarder, and possibly a flow-aid.

[K-nadian]

Hey if you dont mind me interjecting, Im new to the hobby and I'm experiencing some problems while brush painting. Im using Model Masters acrylic and im trying to put down a very light coat of flat black and im getting a crummy texture instead of a nice smooth coat. I admit I have brushed over the area more than once because I thought the first pass left way too much paint behind. Is this the issue this thread aims to fix? Is general consensus in the modeling world that brush painting acrylic is difficult because it dries quickly? Just trying to get a feel for these issues. Thanks.

[MattC]

Is general consensus in the modeling world that brush painting acrylic is difficult because it dries quickly? Just trying to get a feel for these issues

Dry quickly? No, they don't, certainly not when brushed, but they do go tacky quite quickly, but the main issue vs enamels is that enamels, and more especially humbrol (more than others) are very forgiving of overbrushing, and seem to flatten themselves nicely.

In my experience, Acrylics are not "more difficult" just different, as others have said, you can't brush them out like you can an enamel, and you really do need to give them plenty of time to go off before recoating.

Generally, I have found acyrlics to be more of a pain than they are worth for brush painting, the quick drying speed isn't such an advantage with a brush, whereas with an airbrush you can shoot a second coat over the first reasonably quickly, you just can't with a brush, it makes a mess.

Edited April 16, 2011 by MattC

[Triarius]

Acrylics generally do dry faster than enamels, but they don't cure as rapidly. That means they reach the tack state quickly, but stay tacky longer, and don't achieve full bond to the underlying material for longer than enamels.

The rapid drying is addressed by using small amounts of acrylic retarder, and for some brands (Tamiya, Gunze for example) small amounts of an appropriate thinner.

Using these methods, brushing them is no harder than brushing enamels, just different.

[K-nadian]

Hey thanks guys. In contrast to what you said MattC, when I brush my acrylic on, it is dry within a minute - two minutes. I'd consider that really fast. By dry I mean to the touch. I understand its still not cured to the surface, but nothing rubs off when i touch it. Ill take the advice you both give and wont brush over a surface more than once, and give coats sufficient time to dry.

Case in point, Im doing up the burner cans on my CF-18. Im coating them in flat black acrylic, then coloring them in plain old pencil lead, which i then rub with a q-tip to take some shine away and gives it a darker gunmetal shade. It looks beautiful... on the one can I managed to complete. As you can imagine, for the smooth surface of the petals on the can I want the flat to go on as smooth as possible, but on my second can, im getting a crummy texture in the black, which ruins the effect of the pencil finish. I just thought I had good luck on the first one, but Im learning that im giving the surface too many passes. Inexperience - but a good learning experience.

Can you explain just exactly what you mean by the "tacky" stage? Do you mean dry to the touch, but not cured?

Thanks guys!

[MikeC]

I'll second OBD's method - almost identical to what I've evolved over the years. I don't bother to wipe the brush on a third palette, because I've never thought of it, perhaps I should ...

[-Neu-]

I may differ with some opinions here but I've found that Tamiya paints are actually very poor brush paints. They go on too thin and you can't put a second coat down because the new layer will ruin the first one's finish. That said Tamiya paints are the best in my mind for airbrushing.... they go on extremely well. I've actually taken to buying a range of Vallejho paints for hand brushing, while using Tamiya exclusively for the air brush.

[-Neu-]

Double post

Edited April 17, 2011 by -Neu-

[Triarius]

Can you explain just exactly what you mean by the "tacky" stage? Do you mean dry to the touch, but not cured?

There are stages to a coatings behavior on the surface:

flow stage: paint is on surface and self-leveling; has begun to lose solvent.

tack stage: paint is still plastic, deformable but will not flow, and the surface is sticky; solvent loss continues, substantial solvent remains

tack-free stage: paint is still plastic, deformable but will not flow, surface is not sticky, solvent loss continues, minimal solvent remains

initial set stage: paint is dry to touch but not fully cured; solvent loss continues but little remains

final set (cured) stage: coating formation is complete and little or no solvent remains.

[K-nadian]

There are stages to a coatings behavior on the surface:

flow stage: paint is on surface and self-leveling; has begun to lose solvent.

tack stage: paint is still plastic, deformable but will not flow, and the surface is sticky; solvent loss continues, substantial solvent remains

tack-free stage: paint is still plastic, deformable but will not flow, surface is not sticky, solvent loss continues, minimal solvent remains

initial set stage: paint is dry to touch but not fully cured; solvent loss continues but little remains

final set (cured) stage: coating formation is complete and little or no solvent remains.

Thanks Triarius for clearing that up!

k