Cleaner

Pre-releasing is another issue that has many contributing factors. Mold design, laminate schedule, resin formulation, gel coat formulation, improperly calibrated spray equipment, gel coat cure time, under or over catalization, shop temperature, humidity, and external heat sources – to name a few – can all lead to pre-release. Most semi-permanent mold releases have a lower surface coefficient of friction than conventional paste waxes, which is why they are more often implicated in pre-release. If all factors other than mold release have been addressed, you may be able to reduce the incidence of pre-release by lightly wiping areas where the mold is pre-releasing with a high quality mold cleaner to slightly alter the surface tension.

A lot depends upon the material you are using to patch the mold, how thoroughly the patch material cures, as well as the depth and overall size of the patch. Quick set, talc filled, styrene free, BPO cured putties have advantages in these applications even though they must be over-sprayed with gel coat for a cosmetic finish.

(HELPFUL HINT): Some people find that drilling some small negative draft holes down in the laminate area surrounding the area to be patched helps lock the patch to the mold and reduces the incidence of pull out during the seasoning of the patched area.

Once the patched area has been cured, compounded and buffed, all foreign matter should be removed from the surface using a high quality mold cleaner. Follow this by applying a high quality sealer and release agent following the manufacturer’s instructions.

Sanding, heavy buffing and stripping can open pores of a mold, allowing un-reacted styrene to bleed out of the mold during production. This can occur in seasoned molds as well. Once the mold has been buffed, sanded, or stripped, and all foreign matter removed, clean the mold with a high quality mold cleaner following the recommended application procedure. Then apply a high quality sealer and release agent following the manufacturer’s instructions.

Gel Coat Over-Spray: Gel coat over-spray has been catalyzed. Even if the film over-sprayed on the mold is thin, it will eventually get hard. If the over-spray has not cured it can usually be wiped off with a cloth dampened with a high quality mold cleaner and then followed by a re-application of mold release. If the over-spray has cured, and the mold has release agent on it, it can sometimes be wiped off with a cloth saturated with a high quality mold cleaner and then followed with a re-application of the release. Or, simply let it totally cure and just peel it off the mold surface. If the mold surface has no release on it and the over-spray cures, in most cases it must be compounded off.

Raw or un-catalyzed resin: Dampen a cloth with a high quality mold cleaner and wipe the raw resin off the mold surface. Use as little mold cleaner as possible and as little pressure in removal as possible to avoid removing an excessive amount of release from the mold. However, you must ensure that you totally remove the un-catalyzed resin from the mold surface; since a thin uncured film of resin could lead to problems on the next de-molding. Having removed all of the uncured resin from the mold surface, reapply mold release and continue processing.

By taking a few precautions, you can achieve the same production from these types of surfaces as from a polished smooth surface. Buildup in non-skid areas generally can be seen as the same color as the spray-up gel coat. The cause of buildup in the grooves of the pattern usually result from either: 1) failure to apply the release into the tips of deep recesses in the pattern which causes small bits of gel coat or resin to bond in the tips with each cycle, or 2) excess release agent pooling in these areas because of poor application technique. When excess release is present, it does not have a chance to dry or cure thoroughly, or to develop full chemical resistance. The release films over on the surface and can attract free styrene from the gel coat or resin used to mold parts. This can occur because styrene in the resin acts as a solvent, penetrating the heavier areas of release and accelerating the buildup and sticking in these areas. To reduce the buildup and sticking concerns, care should be taken to thoroughly brush out and polish the release into these deep patterns without leaving a heavy residue.