First of all, just to be clear about what they do/are for, let's start by covering what paint
is.
Paint is basically a very finely-ground pigment suspended in an acrylic binder. The acrylic binder stays wet whilst there is water in it. In addition, other additives may be present in order to give the paint other desirable characteristics (like workability, matte/satin/gloss finish, faster drying time, etc).
The more pigment in the paint, and the more finely ground it is, the more expensive the paint is. Model paint usually have relatively low pigment content compared to artists' acrylics, but the pigments are often much finer.
Metallic paint usually includes mica flakes, which is what reflects light and makes them appear shiny. The bigger the flakes, the "coarser" the "metal" finish appears. Sometimes, real metal is used instead of mica, and often there is a tint added to the flake-binder mixture to make the paint appear as gold or silver or whatever. Real metal is more expensive than mica in such paints, and the binder is sometimes formulated slightly differently too.
Now, each of the more usual additive products will affect one or more paint characteristics differently, and some don't play well together. Roughly grouping them, these are as follows:
Matte/Gloss MediumsIf you think of paint without pigment as "blank", then that's basically what these are - blank paint.
They come in a variety of finishes, usually matte or gloss, but do not change the consistency of the paint.
They do change the finish though - adding a touch of matte medium to regular paint gives the mixture a matte finish for example.
Adding these to your paint reduces the concentration of pigment in the paint, and effectively the paint becomes more transparent. This allows you to layer your colour(s) to build up a desired transition.
Mixing matte medium and gloss medium together causes the paint to immediately "coagulate" and spoil, so don't do it. Adding matte medium to gloss paint is okay, and gloss medium to matte paint is fine too. However, whatever is in the mediums themselves does not allow you to mix them with each other at all.
Metallic MediumsThese are a very small amount of binder with rather a lot of mica.
You add this to inks or to paints to make them "metallic". This works best if the pigment doesn't obscure the flakes too much, so adding them to ink or to a paint-and-ink mixture generally works best. You can also add these to metallic paints to boost how reflective they are, and to brighten them.
Glaze MediumsSometimes known as flow-aids, these are basically an additive that lowers the surface tension in paint to make it more runny. This improves the flow of the paint, reducing tide marks and streaks when you paint in thin layers. It also helps to keep the pigment more evenly distributed when you thin the paint.
Adding a drop of paint to a few drops of glaze medium plus a few drops of matte medium and some clean water allows you to make a GW-style wash in any colour you want.
Quick-dry/RetardersMost craft/hobby/model paints are designed to dry fairly quickly so that painters can do multiple coats in one sitting.
Retarders slow down that drying process, giving you more time to work the paint.
They are useful if you have to freehand small designs or if you want a wash to dry slowly enough to allow the pigment in it to settle in a more graduated manner.
Retarders are often very gloopy though, and are hard to mix into paint. Pre-thinning them with clean water and keeping them in a dropper bottle makes them much easier to use. It also allows you more precise control on the amount of retarder added to paint (if you add too much, the paint will stay wet for days, and will be "tender" for days more).
I don't know of anyone using quick-drying additives with their model paints, but they are available for artist's acrylic paints, and might be useful if you want your paint to dry faster for some reason.
ThinnersUsually, this means clean water. However, adding a lot of water can make the paint take a long time to dry.
Some thinners are basically just alcohol (commonly used to thin metal-flake metallic paints, and also some of the Tamiya model paints), which thins paint and dries very fast.
Some thinners are a mixture of alcohols and water though, allowing you to really thin paints without increasing the drying time too much as a result.
Some thinners are also useful/used as flow-aids too.
For thinners, there is another reason that you might not just use water, and that is that if you thin the paint too much, you can "break" the binder's capacity to suspend the pigment properly within it. If this happens, it'll make the paint harder to work with - not least because many of the pigments will settle out of the paint pretty quickly then, and can even give you a "gritty" texture.
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Finally, some of the above can be used in other ways too.
For example, using a water and matte medium mixture over a gloss surface flattens the shine totally. This is useful if you want to hand-varnish in gloss for durability, but prefer a matte finish and don't want to re-varnish or spray over.
You can also gently brush some metallic medium along the edges of a painted metallic surface as a very delicate "super-highlight" too, although you will need to seal if if the model is for gaming because the binder in the medium is very very light.
I mostly use Vallejo's mediums, glazes, and retarders. However, Liquitex (an artists' acrylics brand) makes a superb matte medium and glaze medium that I know many people use - and a half pint of either will last you
forever too.
It's worth researching into artists' acrylics brands (like Liquitex, Golden, Winsor & Newton, Daler & Rowney, etc) because they are not only often better value, but they also offer other products too. Some of the products like crackle medium or texture pastes might not be too useful for miniatures themselves, but instead might be really good for doing the bases with.
So there you go, a bit of a long-winded explanation, but hopefully that's helped you get a start on what the more common additives do.
09 August 2010, 02:26:32 PM