smoothing corners and gel coating problems

Is there a good method of smoothing fillets and radiuses made using plasticine in the corners of a one shot mould? They look pretty smooth but when you remove the part from the mould after gel coating and glassing they are not very smooth at all, and require a lot of sanding and filling. I also have trouble getting the gel coat to cover the plasticine, should I be using something else instead of plasticine. The mould is made from melamite and only needs one coat of wax to release, for this reason I did not spray the mould with PVA but maybe I need to coat the plasticine with PVA.

Regards
Bruce

 

Bruce, I just use a coin[5,10,20c mostly] a heat gun + single sided razor- warm up your plasticine-roll sausages apropriate to radius-put in corner-blast with heat-thumb in-re blast & swipe with coin at angle-heat blast & swipe with coin square- shave spare cine carfully-swipe wax rag along & blend & lift any stray cine-wax & polish off-ready to shoot.Triple corners are a bit tuffer but just drag your coin out of them.Jeff.

 

If you're going to use the mold more than a few times, Bondo works pretty good. Put it in a plastic sandwich bag, cut off one corner and use it like a pastry squeeze bag thing that is used for writing on cakes with frosting. The correct tool for forming fillets (they make a wax fillet on a roll in various sizes for different size radiuses, a mold tooling product) is a steel ball on the end of a rod. I have one of 1/4" diameter which is just a lifter push rod from an auto engine, I have a few others of different sizes I made by welding a ball bearing to the end of a rod. This is the best tool for the triple corners Waikikin is refering to. It works on plasticine too. I've never tried the wax and I usually can't find the ball bearing things when I need them so what I do is roll a small blob of the clay between two formica covered boards until I get a piece about a foot long and the correct diameter, stick it in the corner with my fingers and then drag at a slant a waxed socket from the tool box over it. The sockets are any diameter you want and you can attach a 3 or 6" extension to it for a handle. Press hard enough for the socket to ride against the mold, which will leave the excess clay separated from the radius itself by 1/16" or so, which you carefully remove somehow. You can cover the radius with PVA useing a small piece of upholstry foam to wipe it on or a small brush. Sam

 

the plastercine has a lot of oil in it so use pva to seal it in