Wednesday, April 21, 2021

A Guide to Hobby Paint Types and Solvents

Palate, Pilate, Pallete

So, you’ve decided to finally get your hands dirty and paint a Gunpla kit. Now, you wonder what paint to use, and if you screw up, what solvent to use to strip the paint. Here’s a quick guide on Paint Solvents (which ultimately, determine the paint type) and their effect on plastic in general.

So, you’ve decided to finally get your hands dirty and paint a Gunpla kit. Now, you wonder what paint to use, and if you screw up, what solvent to use to strip the paint. Here’s a quick guide on Paint Solvents (which ultimately, determine the paint type) and their effect on plastic in general.

Paint types - Paints are categorized mainly under three types, and they are called as such because of the additive in the paint.

  • Acrylic - Acrylic paints are acrylic-resin pigment-type paints suspended in a polymer solution and is usually water-soluble. These paints become water-resistant when dry and are highly durable. Some Acrylic paints are alcohol-based. Depending on their formulation, water-based acrylics can be thinned with alcohol and vice-versa.
  • Lacquer - The term lacquer originated from the lac insect with secretes resinous shellac, which were used in olden times to coat wood to protect them from the elements. Lacquer can also be drawn from the resinous sap of some trees. Lacquer paints are made by mixing pigments with lacquer, and is mostly alcohol-based.
  • Enamel - Enamel paints are oil-based paints that usually dries with a certain gloss.

Base types - the base of a paint is the solvent use to suspend or dissolve it, as such, the base of a paint is also its thinner, or reducer. As such, there’s no such thing as acrylic-base paint.

  • Water-based - Acrylics paints are mostly water-based, hence can be thinned or diluted with plain tap water, although distilled or filtered water works best, since those do not have particulates that paint tend to clump onto, which is what happens when paint clumps onto your brush.
  • Alcohol-based - Some acrylics and lacquers are alcohol-based (or ketone-based), mostly plant distillates (ethyl). These types dry slightly faster than water-based paints, and often also water-soluble.
  • Oil-based - Enamel bases are often oil or mineral spirits or combinations of it. Among these are turpentine, safflower and other plant-oils.

Solvents/Thinners/Strippers

  • Water - The Universal Solvent. Some, if not most acrylic paints, especially the ones designed for hand painting, are actually water-based and can be diluted or thinned with plain tap water, but ideally, distilled or filtered water is better since tap water contain micro-particles that causes paint to clump, especially when hand-painted. It can’t strip paints, even water-based acrylics, and is very safe on all types of plastics.
  • Denatured Alcohol - Used mainly in cosmetics and perfumery, Denatured Alcohol is general purpose and can be used for both thinning Acrylic paints for airbrushing or stripping most types of paint. Not to be confused with 70% rubbing alcohol (isopropyl, which is petroleum-based, or ethyl, which is plant-based), though certain paints can be thinned and stripped-off with rubbing alcohol. Alcohols are safe on all types of plastics. Denatured alcohol can be used for soak-stripping. Denatured alcohol is mostly ethanol (or ethyl alcohol at high concentration) with impurities mixed in to make it unfit for human consumption.
    There’s also denatured-alcohol available in hardware stores, but these are weaker and does not strip as well as the medical grade, which is 95-99% pure.
  • 99% Isopropyl Alcohol. Used mainly in laboratories and hospitals for general disinfection, this alcohol is rather strong and can strip off most paint types, and also safe for soak-stripping.
  • Acrylic Thinners - These type of thinners are alcohol-based (combined with other ketones) and can be used to thin and strip paint. Even though it’s alcohol-based, the other chemicals in certain acrylic thinners react to and can damage ABS plastics, making them brittle over time, so it’s not advisable to soak plastic parts for when stripping paint.
    You can make your own acrylic thinner using alcohol and 3 other chemicals.
  • Lacquer Thinners - Lacquer thinners are usually made with ketones, like acetone, toluene and methanol (alcohol) and have close analog or compatibility with acrylic thinners which are also mostly made with alcohol.
  • Enamel Thinners - Made with oil and mineral spirits, like turpentine (used on oil-canvas paintings). Enamel thinners are generally safe for most plastics, though like acrylic thinners, is not recommended for soak stripping.
  • Paint Thinners - Hardware store paint thinners are used to thin industrial-type enamel paint (the ones used for painting houses and buildings). I have seen some people claiming to use these regular paint thinners to thin hobby-grade paints, but, it’s best you test it out yourself (will update if I ever do test this myself).
  • Bleach. Bleach can be used for general cleaning (removing yellow stains on plastic) and stripping off chrome/gold plating, but not for thinning.
  • Dot4 Brake Fluid. The strongest of all solvents on this list, brake fluid is not used for thinning, but it can strip off all types of paint from plastics completely, even chrome or gold plating. It can be washed with water, but, the main drawback is it’s highly toxic. Using gloves is recommended, and utmost care must be employed in handling and disposing it. As an advantage, Brake Fluid is reusable, and can be filtered through regular coffee filters. There are some brands of Dot3 brake fluid that can also strip off paint, and it’s not the same across the board.
  • Acetone. Acetone can be used to strip off superglue remnants, but, is very harmful to plastics, especially polystyrene. Avoid at all costs.
  • Hobby-Grade Paint Strippers. There have been at least a couple of hobby-grade paint thinners which supposedly can strip paint clean off parts without damaging the plastic. Though their formulation are being kept secret, these strippers are most probably made with denatured alcohol (or a form of high-percentage alcohol) and plastic safe-ketones.

Paint Coats and Layering

You can combine (as opposed to mix) paint types as you work with them in layers. Here’s a quick layering guide, courtesy of OtakuRevolution.

Simply put, whereas there are lacquer topcoats that can be safely used over acrylics and enamels so as long as they are spray paints or applied with an AB, there are certain lacquer topcoats with strong solvents that can eat through or affect acrylics and enamels especially when handbrushed. It’s best to test the paints and thinners you have on scraps.




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A Guide to Hobby Paint Types and Solvents

Palate, Pilate, Pallete So, you’ve decided to finally get your hands dirty and paint a Gunpla kit. Now, you wonder what paint to use, and if...