Waterslide decals are thin printed films that slide off a backing sheet once soaked in water. They are thinner, more flexible, and more realistic than the dry-rub or sticker decals included with most entry-level Gunpla kits. Many RG and MG kits include a waterslide sheet, and aftermarket sheets are available for nearly every popular suit. Applying them takes patience but no special talent, and the result is markings that look printed onto the armor rather than stuck on top of it.
This guide covers the entire process, from preparing the surface to sealing the finished decals so they last for years on the shelf.
Waterslide vs Dry Transfer vs Stickers
Stickers are the thickest option. They have a visible edge, peel over time, and look obviously applied. Dry transfer decals are rubbed onto the surface and sit flatter, but they are fragile and do not reposition once placed. Waterslide decals are the thinnest and most forgiving: they can be repositioned while wet, conform to curved surfaces with setting solution, and become nearly invisible once sealed. If you want professional-looking markings, waterslides are the standard.
What You Need
Gather these supplies before you start:
- A shallow dish of room-temperature water
- Sharp hobby scissors or a craft knife
- Fine-tipped tweezers
- A soft brush (a small flat watercolor brush works well)
- Mark Setter (or Micro Set) to help adhesion
- Mark Softer (or Micro Sol) to conform decals to curves
- Cotton swabs for blotting excess water
- A gloss top coat (for surface prep)
All of these are standard hobby tools that you will reuse on every future build.
Preparing the Surface
Waterslide decals adhere best to smooth, glossy surfaces. If your plastic is bare or matte, spray a light coat of gloss top coat on the area where the decal will go and let it dry for at least two hours. This prevents silvering, a phenomenon where tiny air pockets form under the decal film and create a frosted, silver appearance. On a glossy base, the decal film bonds directly to the surface without trapping air.
If you have already panel lined, apply the gloss coat over the panel lines so the decals sit on top of a unified, smooth surface. The gloss layer also protects your panel lining from the water and setting solutions used during decal application.
Soaking the Decal
Cut the individual decal from the sheet, leaving a small margin of clear film around the marking. Drop it into the water dish for 15 to 30 seconds. Do not leave it soaking for minutes: over-soaking dissolves the adhesive and the decal will not stick. You want the film to loosen from the backing paper just enough to slide when nudged. Test by gently pushing the edge of the film with your tweezers. If it slides, it is ready.
Positioning and Sliding
Lift the decal and its backing paper from the water with tweezers. Hold the backing against the model where you want the decal to land, then use a damp brush to gently slide the film off the paper and onto the plastic. Once the decal is on the surface, you have a window of 30 to 60 seconds to reposition it while the moisture acts as a lubricant. Use the brush to nudge it into perfect alignment. When you are satisfied, blot the surrounding area with a cotton swab to remove excess water.
Using Mark Setter and Softer
Mark Setter is applied before or under the decal. It contains a mild adhesive that strengthens the bond between the decal film and the surface. Brush a thin layer onto the area before sliding the decal into place. Mark Softer is applied after positioning. It contains a solvent that softens the decal film, causing it to relax and conform to surface contours like raised edges, panel lines, and rivets.
Apply Softer sparingly with a brush, then leave it alone. Do not touch or reposition the decal while the Softer is working. It takes five to ten minutes to dry completely. If the decal still bridges a gap after the first application, add a second thin coat and let it dry again. For aftermarket decals, Softer is especially important because these sheets often have thicker carrier film than Bandai's included decals.
Sealing Your Decals
Once all decals are placed and fully dry (wait at least four hours, preferably overnight), seal the entire model with a final top coat. This locks the decals in place, protects them from peeling or scuffing, and unifies the surface finish so the decals blend seamlessly into the surrounding plastic. A matte coat makes decal edges almost completely invisible. A gloss coat preserves the color saturation of the printed markings.
This final seal is essential. Unsealed decals can lift at the edges over time, especially in humid environments. The top coat creates a permanent bond between the decal, the gloss base, and the environment.
Troubleshooting Common Problems
Silvering
Tiny air pockets trapped under the decal. Caused by applying decals to a matte or rough surface. Fix: apply to gloss only, and use Mark Setter to eliminate gaps. If silvering has already occurred, a careful application of Mark Softer over the affected area can sometimes re-seat the film.
Decal Curling or Tearing
Old or improperly stored decal sheets become brittle. If a decal curls or cracks during soaking, soak it longer and handle it more gently. A drop of Mark Setter in the water can help soften aging film. If the sheet is badly degraded, aftermarket replacements are available for most popular kits.
Decal Sliding Off After Placement
Not enough adhesive. This happens when the decal is over-soaked or the surface is too wet. Blot excess moisture immediately and apply Mark Setter under the decal to add grip.
Final Tips
Work on one area at a time. Place all the decals for a single limb, dry them, then move on. This prevents accidental bumps that shift placed decals. Always refer to the placement guide included with the decal sheet; even a slight misalignment looks wrong once sealed. And remember, panel lining goes on before decals. The recommended order is: build, panel line, gloss coat, decals, final top coat. Following this sequence gives you a clean, professional finish with every marking locked permanently in place.