Right, as promised. This is straight out of the mould, literally dropped it out and took these photos. No cleaning up, no polishing, no top coat. 

Hi Hanaldo, thank's for taking the time to post the pictures.

I suppose much depends upon personal expectations. It may be the light but the spray tack appears to have dulled the surface finish which is exactly what my tests showed. On a highly polished mould, which yours appears to be I would expect a gloss finish straight from the mould.



Without spray tack I get the above finish straight from the mould. As soon as I use spray tack (I've tried several) the same part from the same mould becomes dull requiring additional finishing. That is why I am skeptical about manufacturers claims that it does not have a detrimental effect on surface finish.

Carbon Copies Ltd

Sorry, should have clarified that. I don't have very high gloss moulds because I blend my own tooling gelcoats using ordinary vinyl ester laminating resin and various additives/fillers. While this allows me to produce a tooling gelcoat to the specs that I am happy with, it doesn't have the high gloss additives that allow me to polish it to anything beyond just a reasonable gloss. So what you see there isn't because of anything the spray adhesive does, it is the same standard as the mould surface. 

I didn't realise accessing materials was such an issue for you. I know of a couple of companies doing prepreg parts in Australia, not sure where they are in relation to you but it would be interesting to know what they are using for moulds.

They are accessible here, the issue is that if you are buying small quantities (read: less than 200L drums) then the pricing is ridiculous. I got a quote on 20L of vinyl ester tooling gelcoat, and they wanted $700. It would be better on the east coast, but here on the west coast there just isn't really an industry. 

Hanaldo and Warren, thanks for going to the effort of testing and posting results. I find carbon to be really difficult to take photographs that show the part as seen in person. So I suppose this will make things difficult to prove one way or the other.

Even with 3M Super 77 all I ever needed to do was wipe the surface with acetone and then polish. 

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

Totally agree, I think in mould coatings are the way to go. I use Duratec Sunshield myself, and I love it. The only parts I don't use it as an in-mould on are ones that require secondary bonding, as then I am going to bond them together, clean up the split line and spray the Duratec as a top coat. The wonderful thing about Duratec is its high-build properties mean it's very easy to fill imperfections and you can make bond lines virtually invisible. 

Yes I can see how in-mould coatings will have a better long term chemical bond than clear coat. I even have GC50 in the cupboard. After I bought it I realised it needed to be sprayed and it sounded like the correct spray technique took a few attempts to master. I want to be able to make a mould and do one infusion from it then move on. No experiments or failed attempts.