Resin casting FYI



For some of you, this post is going to be "No ****, Sherlock", but I wanted to share a revelation I had recently concerning resin viscosity and casting results during the slush molding process.

Previously I had been using SynAir's Por a Kast MK I resin, off white in color and a tiny bit heavier than the pure white MK II. In the middle of last year SynAir ceased the production of the MK I because one of their suppliers who was the sole source of a key chemical used in it's manufacture, no longer made the stuff. SynAir was looking to create a new formula when the Por a Kast line was sold to a British outfit by the name of Hyperlast (

I then switched to Por a Kast Mk II which was still available from other carriers. When it was time to reorder I switched to Smooth Cast 320 from Smooth On ( It is very much like the Por a Kast MK I that I had liked------and here's where I finally land the plane on this trip!------depending on which of these two resins are used, the rotational speed of the mold during casting determines how well the pull will turn out. Because the Por a Kast MK II is more "watery" a faster rotation is required, while the Smooth Cast 320 which is thicker, needs a slower rotation I found.

So, there you have it, my little resin "epiphany".