Hi Craig, as you say its difficult to get it to show in a photograph. The spray tack is clearly visible on the surface if you look closely, if removed with acetone you are left with very small low spots in the epoxy where the spray tack has been. This can be rectified with a clear coat but for me that defeats the object.
The reason I spend time on plugs and moulds is so that the part can just be pulled, trimmed, and its ready to go. Adding more time clear coating is a commercial no no for me. You can easily add 2/3 (more on large parts) hours work clear coating which eats into profits and can make the finished costs too high for market.
If you are not meticulous at removing every bit of release agent, key the surface and use an adhesion promoter clear coat can fish eye or cause pin holes either ruining an expensive part or meaning even more additional work is required. If you don't bake 2k it's not particularly tough or hard wearing either.
If a part requires UV protection I use GC50 in mould clear gelcoat. I know it requires spray equipment but so does 2k. If something goes wrong during application you can let it cure then remove it from the mould and start again before using any expensive carbon etc. You can also use virtually any spray tack as it wont affect the surface finish ( I use standard 3m spray mount found in craft stores) or you can actually use the GC50 as a spray tack for the first layer of carbon if you get the timing right. Unlike applying 2k post infusion which will only have a mechanical bond, GC50 will chemically bond to the epoxy and is much tougher/durable. As with most things there are pros and cons, it does mean the infusion has to be spot on as there is little chance of repairing flaws under the gelcoat.
I appreciate for home projects where time is effectively free 2k clear may be the answer but from a commercial side GC50 wins every time.
Warren
Carbon Copies Ltd