Re: [ATM] Stuck 20" lap on 30" mirror

["Stars" <rocketmaker@intergate.com>]

I use saran wrap or similiar between the pitch and glass when cold pressing 
for long periods. -Rick


----- Original Message ----- 
From: "Bill Prewitt" <bprewitt@neo.rr.com>
To: "ATM List" <atm@atmlist.net>
Sent: Thursday, November 01, 2007 6:03 PM
Subject: [ATM] Stuck 20" lap on 30" mirror


> I've been traveling a lot lately, and have only been able to work on
> this figuring project for a few days every month or so. Last month, I
> poured a fresh layer of Gugolz 55 on a 20" lap, and left it to cold
> press till I came back.
>
> Big mistake... It was stuck tight.
>
> To dislodge the lap, I tried bar clamps, tubular webbing with a wood
> lever, then plastic-sheathed steel cable with a metal lever for several
> days of sustained force, but nothing worked.
>
> So yesterday I bought 10 pounds of dry ice, layered it on top of the
> lap, and covered everything with towels and blankets. After 24 hours of
> chilling under tension, the lap separated easily from the mirror.
>
> The lap surface was shiny & black.
> I had forgotten to coat the face with CeO before pressing.
>
>      Bill Prewitt
> ----------------------------------------
>          www.astrocaver.com
>  webpage of telescope making and caving
>      My hobbies keep me in the dark
> ----------------------------------------
>
>
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> 

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