general questions about acrylics

Please note that I said "hand brushed acrylics" with respect to drying and curing. And even my generalization is not entirely accurate. Acrylics that use alcohols as their dominant solvent dry much faster than those that use more water—and drying is not the problem, it's curing. Until an acrylic paint is fully cured, it's adhesion to a plastic surface may be relatively weak. Enamels bond to the substrate faster, partially because of their solvents, and partially because the binder in enamel has a greater chemical affinity for the plastic.

Model paints are formulated specifically for plastic substrates, which is why craft paints sometimes don't adhere well to plastic. Some acrylic interior house paints can be scraped off styrene with a thumbnail.

And don't feel even the slightest discomfort at a misconception about paint. Paint science and technology is mind-numbingly complex. Libraries have been (and continue to be) written on the subject!

Thanks for correcting some false info.

I had thought (and had no source say differently that i had read or been told) that acrylic paint dryed MUCH faster then enemals period. Since it takes 48 hours to properly dry, i will still only use acrylics when i do not feel ventlation is good enough for enemals (such as moving into a apartment).

As for the paint medium idea, some paints do actually have paint medium avable such as Tri Art: Airbrush Acrylics which will allow for longer storage, but i guess i was mistaken with most (if not all) model brand paints.

I have to disagree. I've been using acrylics almost exclusively for over twenty years, and I used to work in the paint industry:

ZzZGuy wrote:

If your hand brushing acrylic paint for the first time, be warned that when applying serveral layers, each new layer you apply may be striped down to the plastic with the brushing action. Small parts that don't require much brusing are generaly safe. If you do encounter problems, i recommend putting on a clear coat inbetween layers, befor i got my airbrush i used testors dullcoat as it drys very fast and worked good for me (you don't need to use only this brand or type of clearcoat).

I have never had such a problem with fully cured (There is a difference between "dried" and "cured"!) acrylic paint on a clean surface. Brushed coats are generally thicker than sprayed coats, and thus take longer to cure after they have dried.

ZzZGuy wrote:

I recommend enemal paint for hand brushing which i thin and clean the brushes using mineral sprits. The downside is it takes 24 hours to dry properly, <snip>

To cure properly, as do acrylics. In fact, hand brushed acrylics take longer to dry and cure. I'd wait at least 48 hours (varies with temperture and humidity)

ZzZGuy wrote:

<snip>the brand name thinner as this is basicly the paint medium without any color added.

Sorry, that is not the case (although a reasonable assumption). Thinner is solvent, or a solvent blend, possibly with additives (e.g., Tamiya thinner contains a retarder). Paints are formulated with a specific ratio of binder to pigment to solvent. Changing that ratio usually reduces the shelf life of the paint, sometimes drastically. Paints that have been thinned/diluted/"reduced" (the latter is the proper paint technology term) for spraying should not be stored for extended periods of time. They will usually keep for the duration of a single project, provided that project does not run for a month.

-edit- to much stuff i was wrong on, but i still recomend a clear coat between layers if there are problems -edit-

Thanks for your advice everyone, I can't wait to start painting.

Three quick points:

1. Model Master Acryl paints are prethinned already for airbrushing.  You really only to thin them for washes or fineline painting.

2. I have found that it is best to thin Acryl with MM Acryl Thinner not water.

3. Same goes with Testor Enamels.  It's best to thin with same brand thinner as the paint.  If you already have the brush cleaner, I would (and do) use that for washes.

Personally, I use nothing but Testors paints, both Enamels and their Acryl line.

Jesse

1) No. Thin about as much as you need at a time. You can always thin more as you need it.

2) Yes, that will work. You can also use an acrylic wash that is thinned with water over Future, provided that the Future is thorougly cured. If you do this, wipe up the excess wash as soon as possible after application. This is easier if you add a drop or two of soap (not detergent) as a dispersant to the wash. Soap does not affect Future very much, but some detergents will. I use Woolite.

3) Nyet! Nine! Non! No!

4) Wash it down the drain with plenty of water (you don't want it to set up in the trap!) Soap or detergent and water, Windex, and Simple Green are good for clean-up.

5) Why not clean it up with mineral spirits?

Thanks Paul, that was really helpful. I'm picking up some Future asap!

I'm using some metallic enamels (Testors) to paint a car engine. It seems like I can use an acrylic wash directly on top of an enamel finish, is that true?

Thanks again,

Jeff

Hi Jeff,
I can help you with questions 1 to 4. I use acrylics nearly all the time.

1. I don't store pre-thinnned paint for the long run. I just make it up as I go along. Sometimes I want thinner paint than at other times, so it just depends. Never heard of anyone advising to keep pre-thinnned paint.

2. I just airbrush Future on there, then use acrylic washes on top. I am 99% certain that oil washes can go on top of Future as well. (In fact I think just about anything can go on top of Future.)

3. Same as for question #1 but more so. Washes really do vary depending what colour you are putting them on top of. Keeping a set of them ready for use would be really difficult unless you were doing the same coloured things all the time.

4. Acrylics are water soluable. The sink is where I do my clean up at the end of the session.

5. I don't know what Testors' brush cleaner is made of, so can't help you there. Sorry.

Paul