Flash

What is Flash?

Thin silicone overflow or flap that forms at the mold seam during casting and must be trimmed off before the finished toy ships.

How Does Flash Form During Casting?

Flash is the thin fin of excess silicone that squeezes between the two halves of a production mold during the pouring and curing process. Every mold has a parting line where its halves meet, and no matter how precisely those halves are clamped together, liquid silicone under pressure will find the tiniest gap. The result is a paper-thin flap of cured material running along the seam line of the finished piece. Flash is not a defect in itself — it is an expected byproduct of mold-based manufacturing that every hand-poured toy producer deals with on every single unit.

Why Does Flash Vary Between Pours?

The amount of flash on a finished toy depends on several factors. Mold age is the biggest one: a brand-new production mold with crisp, tight-fitting halves produces barely any flash, while an older mold with worn edges or slightly warped parting surfaces lets more silicone escape. Clamping pressure also matters — molds secured with straps, clamps, or bolts control flash better than those held together loosely. The viscosity of the silicone mix plays a role too; thinner, more fluid formulations creep into gaps more readily than thicker ones. Finally, using a pressure pot during curing increases internal pressure on the liquid silicone, which can push more material into seam gaps and produce heavier flash.

How Is Flash Trimmed and Finished?

After demolding, the maker trims flash away using sharp scissors, scalpels, or purpose-built trimming tools. A skilled maker removes flash so cleanly that no trimming marks are visible to the naked eye. The goal is a smooth, continuous surface along the seam line with no raised edges, rough spots, or visible cut marks. On a well-finished piece, you can run your finger along the parting line and feel nothing but seamless silicone. When flash removal is rushed or sloppy, the result is noticeable ridges, rough patches, or even small nicks in the surface — all of which downgrade the toy to seconds status.

Why Is Flash a Quality Indicator?

Excessive or poorly trimmed flash is one of the clearest signs of declining mold quality or inconsistent finishing standards. Experienced collectors inspect the seam line closely when receiving a new piece. A thin, cleanly removed flash line is perfectly normal and acceptable — it is simply evidence of the handmade process. Heavy, thick flash that required aggressive trimming, however, suggests the mold is wearing out and may be producing less crisp detail elsewhere on the toy as well. If you are shopping LustMonster inventory and want to understand what to look for, checking the seam area is always a smart first step in evaluating craftsmanship.