When flipping we place another sheet of fresh PTFE on top of the slab and simply flip everything over(careful to keep loose ends contained! Can be prevented by pressing the layers between a flat object to momentarily hold them in place), and pull away the first sheet, sliding it back onto the original sheet if desired. No reason to flip yet if it isn't stable enough to do so IMO.
basic question: "flip" ?
How do you do this? Is it already so stable that you can just lift the whole piece and flip? Just trying to wrap my head around this, sounds alot easier than scraping a mess.
Great tips on doing the flip in this video by Bret Maverick,
http://youtu.be/PzBdp3JXKTk
The trick of sliding the parchment over the counter top works even better when slid over the edge of a frozen marble slab, gotta beware of the moisture though...
I don't endorse Bret's purge time/temperature/vacuum levels...heck, I'd don't even believe in flipping.....
"Why don't you believe in flipping?"
I bought a couple of books on vacuum technology, and read the molecules aren't just stimulated at the surface, with a thin film like we're using there is no reason to expose the bottom, especially with bottom heat. I wouldn't have mentioned it, except I had an early on experience of shatter autobuttering that I think was caused by excessive flipping, so I'm on the side of the least manipulation during the purge process the better.
I'm with GW that a thin film @ 115F down to -29.5" Hg for less than an hour is all that's necessary for a simple sap/shatter purge, what you do beyond that isn't purging, it's manipulation for a desired effect.
Only way to verify that is send samples to a lab for a residual butane test so you have data to support that conclusion.I'm with GW that a thin film @ 115F down to -29.5" Hg for less than an hour is all that's necessary for a simple sap/shatter purge, what you do beyond that isn't purging, it's manipulation for a desired effect.