FWIW, here is Mike Gretz of Sig Mfg. on canopy materials:

<Ted,
Alan is right on. SIG canopies are not made of butyrate plastic. They are made of PETG plastic.

We haven't used butyrate plastic for at least 10 years, maybe more. If you successfully dyed a SIG canopy in the meantime, you had one that was old stock.

Bottom line is PETG will not accept dye of any sort that we have tried.
On the plus side, PETG is a lot tougher and doesn't get as brittle with age as butyrate plastic, not to mention that it molds easier on our end.

Mike Gretz
SIG Mfg. Co.>