Surface coat is a colored and thickened epoxy product. It is usually brushed into the mold first, then the laminate or casting is done behind it. Once the part is removed from the mold, you'll see the surface coat on the.. yep. You guessed it. The surface.]!
They're all brushable, and usually a little on the fast side (15 to 30 minute work time), but here's the difference between one and the next:
- Heat Resistance
- Abrasion Resistance
Color.. Pretty self explanatory. Heat resistance.. if it's a vacuum forming mold the need for heat resistance is greater. And if this thing you're making is some sort of checking or holding fixture, as in parts are going to be tossed into and out of it regularly, then abrasion resistance is a good thing.
So that's about it. Read the data. Ask questions. Spend money. Life is good!