Thanks, David. I'll try your technique when I get a chance.

Did you learn this by just trying or are you in to other glassblowing?

Have you seen the Youtube channel of Ross North?
https://www.youtube.com/watch?v=3DfPm9IZ1eWoI

Sean


On Wed, Nov 1, 2017 at 2:29 PM, Van Horn, David <
david.vanhorn@backcountryaccess.com> wrote:

> Swirl: Rotate the work around an origin outside it's diameter without
> twisting the work around it's centerline.
> Think "dairy queen ice cream cone top" but sideways.
>
> After this the end will look a bit rough, but after removing excess glass
> with tweezers, continue torching it starting at the tip and it will
> contract into a ball.
> Alternatively for a less pretty but still effective seal, mash it with a
> marver.
> The vac seal was made when you gathered the glass and then did the twist
> and swirl.  This last bit is just appearance/fragility.
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
> Of Sean Breheny
> Sent: Wednesday, November 1, 2017 12:14 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Vacuum plumbing
>
> What do you mean by "swirl"? I have tried twisting but it always seems to
> just make the leak channel a twisted path but not fused together. Also,
> twisting and pulling leads to a very tiny, brittle end to the seal. I was
> able to make it "ball up" a little but never become robust enough that I
> was comfortable it wouldn't break easily.
>
> On Wed, Nov 1, 2017 at 12:43 PM, Van Horn, David < david.vanhorn@
> backcountryaccess.com> wrote:
>
> >
> > Here's the secret:  Once you get it soft, twist and swirl.  This
> > breaks up the leak channel into tiny bubbles.
> > After flame cutting, pull off any excess with stainless steel tweezers
> > and then torch it smooth.
> >
> > I've got that technique down cold, and have done hundreds of such
> > seals without problems, even when running at 50 microns inside.
> > Cooler torches help slow things down, a regular propane torch will work=
..
> >
> >
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