What Is H20 Flat Clear Used For? Aqueous Topcoat Guide
By Panda Hobby - Canada's Largest Gundam Store | Published: 2026-11-04
Category: How-to Guides
H20 Flat Clear is a water-friendly matte topcoat for model kits. Learn when to use it, how to thin and spray it, and how to avoid the common mistakes that ruin a finish.
Quick answer
Use Aqueous H20 Flat Clear as a final matte topcoat to unify decals, protect paint, and remove plastic shine. Apply it in thin, misted layers over fully cured paint, and stop before the surface looks wet.
When a matte topcoat helps and when it hurts
A flat clear topcoat is the right last step for military kits, weathered builds, and any model where you want a painted, non-plastic look. It also seals decals and small paint edges so handling does not wear them away. On the other hand, a matte coat can dull metallic finishes, pearl colors, and clear parts, so mask or skip those areas. If you want a reflective showroom finish, use a gloss topcoat instead and save flat clear for a separate build.
Flat clear vs gloss topcoat: choosing by effect, not by habit
Gloss topcoats deepen color and reflect light, which suits car models and clean science-fiction builds. Flat clear scatters light for a dry, scale look. The two are not interchangeable on the same surface without planning: layering flat over gloss is fine, but gloss over flat will not restore a mirror shine unless you build up several wet coats. Decide the final effect before you start decaling so you do not trap yourself in the wrong finish.
Airbrushing flat clear: thin it, but do not over-thin
Aqueous Hobby Color can be diluted with water, which makes cleanup easy, but water alone can make the coat run or dry grainy. Start with a small test cup and add thinner gradually until the mixture moves like skim milk. Spray at low pressure in light passes rather than one heavy coat. Because the solvent is mild, you can build several thin layers without melting the paint underneath, but you still need to let each layer flash off before the next.
Step-by-step: applying H20 Flat Clear
- Confirm the paint is fully cured: Wait at least 24 hours after the last color coat or decal softener application. Test a hidden area with a light swipe of a cotton swab; if color lifts, wait longer. Common mistake: spraying over paint that is dry to the touch but still soft underneath, which traps solvent and causes wrinkling. If you can smell fresh paint, it is not ready for topcoat.
- Mask clear parts, metallic areas, and joints: Use masking tape or putty to cover clear lenses, exposed metal finishes, and any joint that needs to move. Flat clear will fog clear plastic and kill metallic shine. Common mistake: skipping masking because the coat looks thin, then finding a cloudy canopy after it dries. Mask first, then mix your paint so the tape has time to seal.
- Thin a small test batch: Mix H20 Flat Clear with water or a compatible acrylic thinner in a separate cup, adding thinner a few drops at a time until the consistency is like skim milk. Spray a test card or plastic spoon. Common mistake: thinning by eye in the airbrush cup, which makes the ratio impossible to repeat. Write down the ratio that worked on your test piece.
- Spray light mist coats at low pressure: Hold the airbrush 15–20 cm from the model and apply two or three thin passes, letting each pass flash off until it looks slightly satin. Keep the surface moving and stop before it looks wet. Common mistake: chasing a wet, glossy layer in one pass, which causes runs and pools in panel lines. If a run starts, do not wipe it; let it dry and sand it back later.
- Let it cure before handling: Leave the model in a dust-free spot for several hours, ideally overnight, before reassembling or posing. Flat clear can look uneven while drying. Common mistake: touching the surface after 20 minutes to check the finish, which leaves fingerprints in the soft coat. Plan your topcoat session for the end of the day so the model can sit undisturbed.
Product facts
- Aqueous - H20 Flat Clear (Primary): Aqueous H20 Flat Clear is a water-dilutable hobby paint with a mild solvent and a glossy finish in the bottle. You can clean brushes and thin the paint with water before it dries, but the final flat look only appears after the coat cures, so do not judge the finish while it is still wet.
Aqueous - H20 Flat Clear (Primary)
