sorry if this has been asked before but i have searched the forum but to no avail

i,m about to make a mould using E.Cs Epoxy Mould Making Starter Kit . i will be moulding around a small polyester fibre glass plug

id like to know what steps i need to take before putting the two together

i,m ok in understanding the basics of getting the surface to an excellent finish i.e sanding,polish, compound, etc.

but unsure what i need to cover or paint the surface of the plug with prior to smoothing and polishing

i bought some rustolem plastic primer which says its good for use on polypropylene, polystyrene, resin, PVC, fibreglass and vinyl plastics.

but would it react to the epoxy mould putty

any help appreciated

ideally you should use a 2k paint (2 pac) this dries by a chemical reaction and provides a good hard durable base, any paints that dry by solvent evaporation take weeks to completely dry out.

you can get primers and paints in a rattle can that are 2k, personally i had my plug done in a 2k primer at work then flatted and polished the primer rather than using a coloured paint on top

If you use a good coat of PVA it will isolate anything. I don't spray it, what I do is with a soft cloth bunched up I dip it into the PVA and message it in until it leaves a nice shiney coat. (as it evaporates it will lay down without the dreaded fish eyes)  just keep gently rubbing it in. When it starts to drag stop. It also would help if you put on a few coats of mold release wax on before the PVA.

The PVA will not let you capture a perfect high gloss finish from your plug but thats OK because you will be wet sanding and polishing your mold.

Hope this helps.

Fred    

thanks guys

i actually did both of the suggestions in the end

i got a tin of Spraymax 2k primer , which laid down really smoothly i only had to T cut to bring it to a mirror finish

then i did the PVA the way Fred mentioned after a few coats of wax

and Bob was my uncle a near perfect release. i say near perfect,

 i have two milled 16mm dia flat bottom holes about 5mm deep in the plug which kept hold of the gel coat when i removed the plug from the mould. i may have left the gel coat too long before applying the mould putty i,m not sure, but i now have two 16mm circles in the mould where the putty is exposed and cant think of a way to rectify them........ bummer

thanks again for both suggestions

No worries anything can be fixed. I am not sure what has gone wrong but if some of your gellcoat has stayed with the plug just mix up some more and brush it on the damaged area in the mold. (after you clean with acetone and rough up with sand paper) then when cured sand to shape and polish it out

Fred