Tutorial: Paint Additives & Mediums

After reading the Paint tutorial, I'm sure a few of you have take a trip or two over to your local art store and have inevitably come across the paint additives section. The array of paint additives (everything from making your paint look like water to making it look like sand) can be a little bewildering.

Hopefully, this can answer some of your questions. Before I start I should mention that this isn't meant to be a complete, exhaustive list of every single additive, but a general overview of the most commonly available types.

Should I Add to a Paint or Palette?

As a general rule, most mediums are almost always added to paint to change its properties. As with most things, follow the directions as indicated on the additive's container.

If an additive directs you to add to the paint, it's almost always better to pour the additive out unto a palette and then pour the paint into it. Start by adding a smaller amount than you think you'll need. It's always better to simply mix more needed paint, then to have extra left-over and be unusable. Mix to the correct consistency and you're ready to roll.

When finished, unless stated otherwise, it's not a good idea to add the mixture back into its paint pot.

A Word On Flow Improver

I've already covered the basic on the use of flow improvers/aids in the Brush Care 101 tutorial but thought I'd add the following...

Flow Aids/Improvers should NEVER be added directly to anything other than regular water! In a shining example of dumb-assery, when I first started painting, I added Flow Aid directly to several pots of Citadel paint. After a few days, they didn't cover well. After a few weeks, some form of chemical mutation occured in the depths of my paint drawer and the paints had to be thrown out. Let us never speak of what horrors I witnessed upon opening those jars...

Make sure to add Flow Improver in the recommended ratio. Too much Flow Improver can cause paint to run, cure slowly, and can 'gum-up' brushes. Additionally, flow improvers/aids should only be used with water-soluble paints.

Also, be aware that a few companies label flow improver/aid as "Extender", which can be confusing as some companies label their Retarder as "Extender" as well. A quick look at the directions will clear things up as:

Flow Aid/Improver = "...add to water"

("True") Retarder/Extender = "...add to paint (or palette)"

Gesso & Priming

Gesso is traditionally used as a surface primer for fine arts applications, usually for adding 'tooth' to the surface of canvas panels. Gesso isn't a paint additive per se, but I've included it here since it's generally in the same area as other paint additives.

Modern gesso is generally an acrylic-based medium that contains large particulates. When applied to a smooth surface and cured, the gesso performs the same type of function that spray primer does, without the harmful chemicals. Additionally, unlike spray primers, gesso retains some absorbency (making it perfect as a ground for wall paintings) however, it lacks the resilience of an enamel spray primer.

Hearing all this you may think "sounds like a great way to primer miniatures indoors!" and you may be right, especially considering there are a number of colored gessos on the market currently.

The problem with using gesso as a primer is two-fold. First, gesso is both absorbent and gritty, causing your final paintjob to be both dull and to have a rough texture. Secondly, due to its acrylic nature, gesso doesn't form the same shell-like coating that spray primer does, so that model won't stand up to the abuses of gaming.

Acrylic Matte/Gloss Medium/Gel

As the name suggests, these mediums either add a matte or glossy finish to the fully-cured paint.

These additives have a gel consistency and should be mixed to paint according to the manufacturer's suggested ratio. Be aware that adding matte/gloss medium tends to decrease the opacity of the paint and also works as a Retarder/Extender.

These mediums are airbrush-friendly (in fluid form) and clean up with water.

Gloss, Satin, or Matte Acrylic Varnish & Remover

NOT to be confused with Matte/Gloss Medium, these varnishes are not technically 'additives', as they are never mixed into paint or water. Instead, these work by being painted, brushed, or sprayed over the finished paint to add a particular finish.

Varnishes are useful as they protect the underlying paint from damage, dust, and oily fingers. Be aware though, that adding too much can make the underlying paintjob look less realistic. For example, if you are attempting to paint some spit-shined black boots, gloss medium added to the paint will provide just enough shine, without overwhelming the effects underneath. Varnish will not.

Acrylic varnishes are airbrush-friendly (in fluid form) and clean up with water. make sure all underlying paint is fully dry and cured before applying varnish

Varnish Remover will remove varnishes without harming underlying paint.

Retarder/Extender

Paint Retarder is added to paint to extend its working time before drying/curing. This is useful if you plan to make extensive use of a "dry" palette, as the paint will not dry directly unto the palette.

These additives have either a fluid or gel consistency and should be mixed to paint according to the manufacturer's suggested ratio. Be aware that adding retarder/extender tends to decrease the opacity of the paint.

Acrylic retarders are generally of a fluid consistency, are airbrush-friendly, and clean up with water. This is one of the few additives you can pour back into the pot without adverse effects.

Oil retarders are can be either fluid or gel consistency (though gel is prefered), are NOT airbrush-friendly, and clean up with turpenoid/mineral spirits.

Drying (or Drier) Medium

Drying medium has the reverse effect of retarder, quickening the drying time of paint. As far as I know, it is only found as an oil paint medium, as oil takes so long to dry without it. The primary ingredient of this medium is either a quick-drying resin or chemical (such as cobalt or zinc).

These additives have either a cream or gel consistency and should be mixed to paint according to the manufacturer's suggested ratio. Be aware that adding drier medium tends to decrease the opacity of the paint.

This medium is NOT airbrush-friendly and cleans up with turpenoid/mineral spirits.

Effects Medium - Crackle

This medium allows you to get "crackling" effects within the paint itself, which can be very useful when painting old buildings or vehicles. Be aware that there is both a medium and a varnish with this effect, so be sure to read the product directions!

This medium has either a fluid, gel, or paste consistency and can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Crackle medium is (generally) NOT airbrush-friendly and cleans up with water. Crackle medium should, under no circumstances, be added back to the original paint pot!

Effects Medium - Glazing

As the name implies, glazing medium is useful for glazing techniques.

This medium has a fluid consistency and should be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Glazing medium is airbrush-friendly and cleans up with water.

Effects Mediums - Pearlescent/Iridescent/Glitter

Admit it. You've seen all those tricked-out paintjobs on cars and wondered "how do they do all those effects...and how can I paint that?" These mediums are how. You're welcome.

The Iridescent/Pearlescent mediums have a fluid consistency and should be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

The Glitter Medium is generally a varnish or glaze applying over all other paint.

All these mediums are airbrush-friendly and clean up with water. They are more often than not found in the airbrush section of most art stores, where they get the most use.

Effects Mediums - Water

Depending on the industry the manufacturer caters to, these mediums are known as either "Water effects" (miniatures/models) or "Pouring/Self-Leveling medium" (arts). Effectively, they have the same application - to provide small puddles, spots, or pools of standing water. It's important to do as much research as you can before purchasing any of these mediums, as all are good or bad at some things.

This medium has a fluid or gel consistency and can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Water medium is (generally) NOT airbrush-friendly and cleans up with water.

Texture Mediums - Modeling Pastes

Modeling pastes are a quick way to add texture or build-up a surface and can be tinted with acrylic paints prior to application. Modeling pastes come in three
consistencies - light, regular, or heavy - and are generally applied with a paint knife or other tool. Modeling paste is somewhat similar to wall spackle in texture, consistency, and application.

This medium can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Paste medium is NOT airbrush-friendly and cleans up with water (before curing).

Texture Mediums - Lava (Rock)

Yes, you did read that right - an acrylic medium that closely resembled tiny black lava rock, especially in miniature. Fairly straight-forward. As far as I know, Liquitex is the only manufacturer who makes this where it's widely available.

This medium can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Lava medium is NOT airbrush-friendly and cleans up with water (before curing).

Texture Mediums - Stucco

As the name implies, this medium gives the effect of a stucco'd surface by suspended sand in an acrylic binder, great for desert buildings and sandy terrain.

This medium can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Stucco medium is NOT airbrush-friendly and cleans up with water (before curing).

Texture Mediums - Sand (Natural & Resin)

This medium is almost identical in composition to Stucco but has a much higher sand to binder ratio. The Coarse or Resin Sand medium has bigger granules added and a resin binder, maikng it thicker, but perhaps unsuited for miniature work. The Light or Natural medium is probably best but I still prefer the ratio in Stucco for modeling work.

This medium can be mixed to paint according to the manufacturer's suggested ratio. Make sure all underlying paint is dry and cured before applying!

Sand medium is NOT airbrush-friendly and cleans up with water (before curing).