You're welcome. Answers as follows:

But what to you mean about "high pressure moulding"?

Moulding processes that use more pressure than just vacuum pressure such as inflatable bladders, expanding cores or Resin Transfer Moulding (RTM) all put a lot more stress on a mould than vacuum pressure does. For these processes you need very strong mould and so an epoxy mould (or often billet aluminium!) is required.

2) I saw the chemical release agent allow to do a few "pulls" before to put chemical release again: will the mould cleaner remove totaly the chemical release agent?

Yes, the moud cleaner will strip off any previous release agents, waxes, pva or anything else. after using the mould cleaner it's like starting again on a new mould.

I don't understand something, you said in the tutorial the spray tack you use actually (not stay z I suppose) need compatible polyester epoxy gel coat, but the resin used is epoxy and not polyester: why the spray tack damage the gel coat (and mould release) and not the main resin (I'm curious ^^)

Well, the spray-tack issue is complicated! I'll try to explain the options and the consequences:

OPTION 1: Use a regular 'spray-tack' (like 3M spray-mount or any number of inexpensive repositionable mount adhesives) or any spray-tacks marketed as 'infusion' tack (but not expressly for epoxy) - these are basically all the same thing.
If you use this on the mould surface there is a danger that they will effect the release agent. They might be OK, they might not. Always use only a very light amount - the least you can get away with. They will always leave a visible dither pattern on the surface of your parts and the adhesive itself will need to be wiped off the surface of your parts. Used internally, within the laminate they will have a slight negative impact on the integrity of an epoxy laminate which could potentially lead to failure and delamination in extreme circumstances but more than likely will not have any noticeable consequences. Always use sparingly.

OPTION 2: Use an infusion spray-tack designed for epoxy infusion (Zyvax Spray-Z, Epox-Z)
These special epoxy compatible spray-tacks are designed to cross-link with the epoxy resin and so will not have any adverse effect on the laminate. Used sparingly on the mould surface they should be almost undetectable but use spraringly. Inside the laminate they cause no problems. For the positioning of the vacuum bagging consumables these epoxy compatible spray-tacks are probably not as good as normal spray tack so it might be worth having both and saving the fancy epoxy compatible one for the laminate and mould surface and using the cheaper standard spray tack for the bagging consumables.

OPTION 3: Use a mix of epoxy resin and metholated spirits sprayed onto the mould surface as a spray tack
This is the DIY option but works well for tacking carbon to the mould surface. Because you use the same resin that you use for the infusion (but thinned slightly) it cross-links completely with the infusion resin and so therefore is pretty much totally undetectable on the part surface. It's not a very good tack option for subsequent layers of carbon or bagging consumables because it takes a lot of prep time and doesn't offer much tack but it is nonetheless a good solution for tacking to carbon to the mould surface.

To do this option:

1. Mix a small amount of infusion resin with the correct amount of hardener.
2. Add about 10-25% of metholated spirits to the epoxy to thin it down.
3. Use a cosmetics bottle with a pump spray to spray a thin layer of the epoxy onto the mould surface.
4. Wait for the resin to cure to a 'B stage' (within an hour or 2) and then use this tacky surface to stick your carbon to.

I hope this explains your options.

Best regards, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales