How come when you infuse Carbon Fibre you dont get print thru but when you Vacuum bag you do ?
Matt 
That’s a trick question.
Typically there is less pressure on the vacuum bag with infusion… even though there may be one bar of vacuum with both set ups you mention… some of the pressure is “spent” forcing the resin into the lamanant with infusion.
You can avoid some print thru by ( if using gel coat) by letting the gel coat cure for 12 to 16 hours before doing the lay up. It probably sacrifices some of the chemical bond between the lay up and gel coat but I have not seen the two seperate from each other.
If you are not using gel coat and are just clear painting the parts after infusion, using a true automotive 2K clear coat will help deminish print thru. Spray on 2 normal coats of 2K clear, let it cure, wet sand it with 320p and then lay down 2 more normal coats. 2K urethane auto paint won’t shrink up like rattle can stuff or polyurethane. Just I wouldn’t recomend using the cheapest 2K clear … Transtar Euroclear or Southern Polyurethanes Inc medium solids clear are both very good and not top dollar stuff. Around $120 for a one gallon kit.
you mean spraying clear into the mold? but since it’s got release agents it will start beading…
I think fastrr means spraying the parts with clear after the infusion,not using it as a gel coat in the mold.I use a PPG clear for this.It is a 2 pack designed for coach finishing so is a bit heavier than one designed for cars
If you don’t release your parts with a silicone based release agent… you will only have to wash the parts with dishsoap and water, lightly scuff them with sandpaper 320 or red scotchbrite pad, then spray the clear on.
You are right some mold releases contain chemicals that paint won’t stick to. I have used TR104 wax and never had paint problems as long as i washed the part prior.
PPG high strength degreaser is very good for wiping down parts before clear coating.Much better than ordinary panel wipe.I am using freekote 770 nc and have not had any problems with the clear not taking to the part.
so youre saying even if a vacuum bagged part has print thru it can still be fixed ?
still a very big learning curve lol
Matt
yeah i use Body’s silicone cleaner before clearcoating, nevermind the mold release, even our fingers can leave deposits on the surface…
The print through should be easy to sand off before you clear coat the part unless it is severe.A slightly heavier coat of clear gel first can help to avoid the print through.
Wet layup open molding, bagging a wet layup, resin infusion, and even closed molding can and will produce print through.
Barrier coat and resin matrix selection have the biggest influence on this. Most polyester coatings and resins will exhibit some degree of print through within a month, if not visible right after demolding. VE coatings and resins are much better with more thermal stability and less shrinkage, and epoxy matrices generally shrink the least.
So, the statement “when you infuse Carbon Fibre you dont get print thru but when you Vacuum bag you do” in the original question is simply not correct. There are many variables.
Is one of those variables Honeycomb Nomex ? I’ve never Infused while using Honeycomb sandwiched between layers…only secondarily added later.
What is involved in the added stiffener/bulker ? Veil needed?
Open honeycombs will not work with infusion for the obvious reasons! And veil doesn’t really help if infused with the rest of the laminate. Veil behind gel coat would work though if laid up wet and allowed to cure.