Understanding Model Paints & Thinners

Understanding model paints doesn’t require a chemistry degree. It does require knowing which paint family you have, which products belong with it, and how to adjust the paint for the job. These decisions affect smoothness, adhesion, drying time, cleaning, and the durability of your finished model.

This guide explains the major hobby paint families, the purpose of thinner and other additives, how to mix paint for brush or airbrush application, and how to avoid the compatibility mistakes that can ruin a carefully prepared finish.

The broad categories below are useful starting points, but names on hobby labels are not always chemically precise. In particular, “acrylic” describes a type of binder, not one universal thinner.

No category is automatically the “best”. Each has products that work well for particular jobs.

For example, a water-based acrylic may be ideal for painting cockpit switches by brush, while a lacquer system may be more convenient for a broad, smooth airbrushed aircraft finish. Your tools, workspace, and preferred subjects also matter.

Don’t Let Similar Paint Names Fool You

Tamiya has sold X/XF colors in more than one paint family in different markets. A number such as XF-1 does not by itself identify the paint chemistry. Look for the full words Acrylic Paint, Enamel Paint, or Lacquer Paint on the actual product.

Likewise, different ranges from the same manufacturer may require different thinners. Brand familiarity is not a substitute for reading the individual label.

Water-based acrylic hobby paints are common in scale modeling, miniature painting, and figure painting. Many are designed to brush smoothly, while others are formulated for airbrush use.

Why Modelers Like Them

• Many can be cleaned from brushes with water before they dry.
• Brush-oriented ranges provide good control for figures, interiors, and small details.
• They are available in a wide variety of military, civilian, fantasy, and general-purpose colors.
• Some product lines are formulated to spray directly from the bottle.

Vallejo Model Color, for example, is designed primarily for brush application. Vallejo Model Air is formulated specifically for airbrushing and can often be sprayed as supplied, subject to equipment and conditions.

A Common Mistake: Too Much Water

Although water is suitable for thinning many water-based acrylics, adding an excessive amount can lead to poor coverage, uncontrolled flow, or changes in film performance.

A manufacturer’s acrylic thinner may help maintain the paint’s intended behavior better than arbitrary amounts of water, particularly for airbrushing.

If a paint is already ready to use, don’t thin it merely out of habit.

What to Watch For

Some water-based acrylic paints dry quickly on the brush or airbrush needle. This can cause visible brush texture or tip dry during airbrushing.

Compatible flow improver or retarder products may help in certain cases, but use them sparingly and only as directed.

Some model paints are described as acrylics and are water-soluble, yet perform best with a designated thinner that contains additional ingredients, including alcohols or other solvents.

Tamiya Color X/XF acrylic paints are a familiar example. Tamiya specifically sells X-20A Acrylic Thinner for its acrylic range.

Mr. Hobby’s Aqueous Hobby Color is another distinct acrylic paint range with its own Aqueous thinner. It should not be confused with Mr. Color lacquer paint.

Why Not Just Use Whatever Is on the Bench?

Different thinner formulations can affect drying, leveling, spray behavior, and compatibility. A mixture may initially look smooth but behave poorly once applied.

You may encounter online suggestions for substituting alcohol or other household liquids. Such substitutions are not universal and can introduce safety, adhesion, or performance problems.

For predictable results, especially as a beginner, use the maker’s designated product and test before experimenting.

Enamel paints were standard equipment on modeling benches long before many modern water-based ranges became popular. They remain useful for brush painting, certain finishes, and some weathering methods.

Traditional hobby enamels commonly use a solvent-based carrier and need a compatible enamel thinner for dilution and cleanup.

Strengths of Enamels

Many enamel colors have a comfortable working time for brush application and can settle into a relatively smooth film. Their slower drying behavior can be useful when painting small details or blending compatible effects.

Enamels are also used in some washes and weathering products, but a weathering wash should not automatically be treated as ordinary enamel color paint. Follow the instructions for that specific product.

The Trade-Offs

• A coating may remain vulnerable to handling or further finishing longer than expected.
• Solvent odors, flammability, and respiratory or skin exposure require attention.
• Enamel thinners are not interchangeable with water-based acrylic thinners.
• Certain aggressive topcoats may damage enamel paint underneath, even after it appears dry.

Humbrol and Tamiya both publish instructions for enamel products. Tamiya identifies X-20 Enamel Thinner for its enamel range; that is not the same product as X-20A acrylic thinner.

Hobby lacquer paints are often selected for their smooth spraying characteristics, fast solvent evaporation, and the durable finishes many formulations can produce.

They’re popular for aircraft, armor, and automotive models, especially when an airbrush is available.

Examples include Tamiya LP lacquer paints and Mr. Color. Each has a manufacturer-recommended thinner system. For instance, Tamiya identifies LP-10 as a thinner for its LP lacquer range, and Mr. Hobby offers Mr. Color Thinner and Mr. Color Leveling Thinner for its Mr. Color products.

Why Experienced Modelers Use Lacquers

• Many spray finely and build smooth, thin color coats.
• Some finishes tolerate careful masking well once properly cured.
• Various lacquer ranges offer useful metallic colors and specialized finishing products.

Why They Require More Care

Lacquer solvents may soften or attack bare plastic, incompatible primers, or earlier paint layers. Heavy, wet passes are especially risky on sensitive surfaces.

They may also present significant vapor and fire hazards. Use spraying equipment, ventilation, and protection appropriate for the exact material; not every hobby spray booth is suitable for flammable solvent coatings.

The most important purchase after the paint may be the correct thinner. It is the simplest way to avoid many mixing and application problems.

These are illustrative manufacturer-product pairings, not an exhaustive compatibility chart. Verify the actual label and current manufacturer directions, particularly for specialized products and newer formulations.

What About Mixing Brands?

Some experienced modelers use cross-brand combinations successfully. That doesn’t mean a substitute is automatically approved or safe for every formulation.

Cross-brand thinning or mixing can produce clumps, separation, poor adhesion, inconsistent color, or abnormal drying. If you’re learning, avoid treating online recipes as universal rules.

These products sit next to each other on hobby-store shelves, but they do different jobs.

Never assume that a cleaner is suitable as a paint thinner simply because both products remove or dissolve wet paint.

Example: Preventing Airbrush Tip Dry

If compatible water-based acrylic paint starts drying on the airbrush needle, you may need to review airflow, spray time, thinning, and equipment cleanliness. A small amount of approved flow improver or retarder may be useful for certain paints.

But if the paint is already separating or spitting, adding random chemicals may make matters worse. Diagnose the cause first.

You may have heard that all airbrush paint should have the consistency of milk or that every paint should be mixed 50/50.

Those shortcuts can be misleading.

Paint viscosity, pigment type, the airbrush nozzle, air pressure, temperature, and the desired effect all influence the useful mixture.

Some paints are already formulated for airbrushing. Others start comparatively thick and require more thinner. A metallic paint may behave differently from a flat color in the same range.

What About Manufacturer Ratios?

Use them as a starting point, not a substitute for testing. For example, Mr. Hobby’s published guidance for Mr. Color has described airbrush mixing at approximately 1 part paint to 1.5–2 parts thinner. Vallejo’s Model Air, by contrast, is generally formulated for spraying straight from its bottle. These are different products with different intended starting conditions.

Follow the current instructions for your own product, because ranges and formulations can change.

Signs of a Good Mix

A workable mixture should:

• Leave the brush or airbrush predictably rather than spitting, dragging, or flooding.
• Cover gradually without forming thick ridges or heavy puddles.
• Stay reasonably uniform without grains, clumps, or separation.
• Preserve panel lines and other fine surface detail.
• Reach the intended finish after the appropriate number of controlled coats.

For brush painting, the goal is control and a smooth, even film. Many brush-formulated colors need little thinning, if any.

Step 1 – Mix the Original Paint

Shake or stir the container as directed until the color is uniform. Paint that has separated during storage won’t behave predictably until remixed properly.

Step 2 – Transfer a Small Amount

Put paint on a clean palette. Avoid routinely adding thinner directly to the entire original bottle because it can change the stored paint’s properties.

Step 3 – Add Compatible Thinner Only When Needed

Start with very small additions rather than a large pour. Mix thoroughly and observe the paint’s movement.

Step 4 – Test on Spare Plastic

Use a primed scrap part similar to your model. A suitable brush mix should flow off the bristles without leaving thick brush ridges or immediately running into every recess.

Step 5 – Apply Controlled Coats

Use a brush appropriate to the area, spread paint with gentle strokes, and avoid reworking a layer as it begins to set.

Step 6 – Allow the Layer to Dry

Follow the manufacturer’s recoat guidance. Build coverage with additional controlled coats instead of a single heavy application.

Watch for Over-Thinning

Paint that forms uncontrollable puddles, takes on excessive transparency, or fails to adhere properly may be too thin, although contamination or poor surface preparation can cause similar symptoms.

Airbrushing depends on paint chemistry, air supply, nozzle size, distance, and how much paint you release. Thinning is one part of that system.

Step 1 – Confirm That the Paint Can Be Sprayed

Check the label. Not every product intended for brush use is suitable for an airbrush, and not every specialized coating should be atomized in a home hobby setup.

Step 2 – Check Your Safety Setup

Use appropriate spray capture and ventilation before atomizing the paint. Review the product’s safety information, including vapor, particle, and flammability hazards. Do not spray a product that your booth or protective equipment isn’t rated to handle.

Step 3 – Prepare a Separate Small Batch

For products that need thinning, put a measured amount in a clean mixing cup. Add the designated thinner in the manufacturer’s recommended starting proportion.

Step 4 – Mix Thoroughly

Ensure the liquid is uniform. If the product forms lumps, curdles, or separates, stop; do not attempt to salvage an incompatible mixture by spraying it.

Step 5 – Test the Pattern

Spray lines and small patches onto spare plastic, a practice board, or an appropriate test surface. Observe flow, coverage, and how the coating dries.

Step 6 – Make Small Adjustments

If the spray sputters or produces an overly coarse pattern, review paint mix, nozzle condition, air settings, and distance. If it runs or puddles, decrease the amount deposited and check whether the paint is overly thin.

Change only one variable at a time whenever possible.

Step 7 – Paint in Light Passes

Work around the model gradually. Allow the product’s required intervals between passes or coats, and avoid drowning delicate detail in paint.

Step 8 – Clean Up Promptly

Empty the airbrush safely and clean with the correct product for the paint you actually used. Follow the airbrush maker’s instructions for seals, needles, and disassembly.

Mixing two colors within the same manufacturer’s compatible paint range is often straightforward, but not every pair of colors, mediums, or special-effect products is guaranteed to behave identically.

Mixing paints from different families is more uncertain.

Do not assume that two paints are compatible merely because both labels say acrylic. Their resins, carriers, pigments, and additives may differ.

A Better Way to Mix a Custom Color

1. Choose paints that the manufacturer identifies as compatible.
2. Mix a small trial batch on a palette or in a separate cup.
3. Record the approximate parts of each color.
4. Check for clumping or separation.
5. Apply to a primed test piece and let it dry completely.
6. Only then prepare enough for the model.

Keep Your Color Records

If you create a useful custom military green, interior gray, or weathered brown, note the colors and proportions.

This helps when you need to touch up the model later or paint additional subassemblies.

A small swatch card can also show the final color over white, gray, or black primer.

Many scale models contain more than one kind of coating: primer, base color, detail paint, decals, clear coats, and weathering products.

Using multiple systems can work very well, but the sequence must be compatible.

Why Problems Happen

A strong solvent in a new coat may soften or lift an earlier layer. Other combinations may suffer from poor adhesion even when no visible chemical reaction occurs.

A protective clear coat may help in an approved system, but it is not an indestructible shield against aggressive solvents.

A Safe Way to Test Layers

• Prepare spare plastic using the same primer and base colors as the real model.
• Let each coating cure according to its manufacturer’s instructions.
• Apply the proposed next product in the same way you intend to use it on the model.
• Check for wrinkling, cracking, lifting, color change, tackiness, and loss of detail.
• If the test passes, proceed carefully with controlled application.

Is It Always Lacquer First, Then Enamel, Then Acrylic?

You may encounter simple rules based on placing the “hottest” solvent first. They can be helpful reminders, but they are not universal compatibility guarantees.

Paint chemistry varies by brand. Some combinations work only with very light coats and adequate curing; others should not be layered at all. For example, Tamiya cautions against lacquer over its enamel paints.

Use product-specific directions and a test piece rather than a blanket formula.

The most carefully mixed paint cannot reliably compensate for a dirty or unsuitable surface.

Before painting, check for fingerprints, sanding residue, glue marks, and other contamination. Correct construction defects and allow washed surfaces to dry fully.

A suitable primer can help create a consistent foundation, especially where the model contains more than one material or has undergone filling and sanding.

Does Every Paint Require Primer?

No. Some paints adhere well to appropriately prepared plastic without a separate primer. Others benefit from one, especially on metal, resin, or frequently handled surfaces.

Read the relevant manufacturer’s instructions and test if unsure.

Don’t Thin Away an Adhesion Problem

If paint beads on the surface or lifts under masking tape, excessive thinning may be only one possible cause. The underlying issue might be surface contamination, insufficient curing, or an incompatible coating system.

Correct cleanup protects your equipment and prevents old paint from contaminating the next color.

Brushes

For compatible water-based acrylics, rinse promptly in water while the paint is still wet, following the product’s directions. A suitable brush soap may help remove remaining residue.

For enamels and lacquers, use the maker-approved cleaner and observe its safety precautions. Keep solvents out of the brush ferrule where practical, avoid prolonged soaking, and reshape clean bristles gently.

Airbrushes

After spraying, empty unused paint appropriately. Use the cleaner specified for the paint system and airbrush materials. Follow the airbrush manufacturer’s instructions when flushing, disassembling, or cleaning needles and nozzles.

Don’t force solvents through an airbrush in an unsafe, unventilated environment. Some cleaners are flammable or create irritating vapors or mist.

Avoid Cross-Contamination

A cup or brush with residual solvent can spoil the next batch of water-based paint. Clean and dry tools appropriately before switching families.

Keep paint thinners, strong cleaning products, and clear water in separate, clearly identified containers. Never use food or drink containers for solvents.

Good storage keeps your supplies usable longer and reduces avoidable exposure risks.

Keep lids tightly closed, wipe bottle rims clean when appropriate, and store products in accordance with their labels and safety data sheets.

A Few Useful Habits

• Store paints away from excessive heat, direct sunlight, and freezing conditions when the product requires it.
• Keep flammable solvents in appropriate original containers, away from ignition sources.
• Label any permitted transfer container clearly; never use an unmarked bottle.
• Keep chemicals away from food, children, and pets.
• Record when a paint has been mixed or transferred to another container.
• Dispose of unusable paint and used solvents according to local requirements and product instructions.

Can You Rescue Thick or Old Paint?

Sometimes, but investigate why it thickened. Pigment settling may only require proper remixing. A coating that has chemically cured, formed a persistent skin, become contaminated, or separated irreversibly may not be recoverable.

Do not pour strong thinner into an old bottle at random. Check whether the manufacturer provides a suitable restoring product or recommends discarding it.

Paints and thinners range from relatively low-odor brush products to highly flammable solvent systems. The correct precautions depend on the actual chemicals and application method.

Brush Painting Is Not the Same as Spraying

Brush painting generally produces less airborne paint than spraying, but solvent vapors, skin contact, spills, and flammability may still be concerns.

Airbrushing creates airborne droplets even when the paint is water-based. Solvent-based products may additionally release hazardous vapors.

Build a Safe Working Setup

Read the label and safety data sheet (SDS), use appropriate local exhaust ventilation and any required respiratory protection, and verify that the spray booth is suitable for the product. A basic dust mask does not protect against organic solvent vapors. An ordinary hobby booth is not automatically rated for flammable products.

Wear appropriate eye and skin protection and keep ignition sources away from flammable materials. Do not improvise with strong household solvents or spray industrial two-part coatings containing hazardous isocyanates in a normal hobby setup.

When in doubt about ventilation, equipment, or protective measures, do not spray the product until you have a suitable arrangement.

Most mixing problems become easier to solve when you identify whether the issue is paint chemistry, technique, surface condition, or insufficient curing.

The Most Important Troubleshooting Habit

Mix and test small quantities first. A spare painted wing, tank panel, or scrap sheet of styrene can reveal a bad paint/thinner combination before it reaches a nearly finished model.