From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Sounds heroic.  I haven't tried the roofing tar, but I've heard it can be
good. I was always skeptical about it's cleanliness, but it sounds o.k.
Keep posting on it so we can learn about this stuff.

Colin

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Matt
Considine
Sent: Wednesday, April 09, 2003 10:31 PM To: atm{at}shore.net
Subject: Re: ATM Pitch




I've been experimenting with asphalt roofing pitch after breaking a pitch
lap.  It seems a little softer than what I was working with, but so far, no
real problems.

FWIW, it came in a 100 pound tube and cost $17.  It melts on a hot plate
and doesn't have any grit in it (at least that I've found so far!).   3/4
of a soup-can's worth of melted pitch provided plenty of
coverage for an 8" mirror.

I used a router to make 1/4" channels in a piece of MDF (I think; it
was like compressed sawdust) and then filled the channels with silcone II
(from Home Depot).  Once it had cured, I cut it into an 8" circle, 
poured the roofing pitch onto a dental stone tool that had been cast on the
mirror (with saran wrap between the two) and then pressed the rubber
channel mold on top of the still-warm pitch.  (A wax paper "dam"
had been taped around the tool).

After it had set, I peeled off the channel mold and did a cold press with
the mirror.  (In hindsight, I needed to press longer, as the center didn't
reach full contact.)

Anyway, I thought this might help someone.  I'm working on finding someone
to characterize the pitch relative to Gugolz, so I can't really be of any
help there.

Regards,
Matt

> With the Gugolz 73 pitch in the classroom, the microfacets never go

away
> unless the lap has sat in a warm car or something for a while.
> Most of the laps that I have to remake are because the lap got
pressed out
> during the week.
> Bob May

--- BBBS/NT v4.00 MP