Re: [ATM] re: Working with thin mirrors

[Woodchuck <djv@bedford.net>]

On Fri, 26 Nov 2004, Ellen Mackenzie wrote:

>     One item that I never see mentioned is sealing wax, the kind Lawyers use
> to "seal" a document. It is a great material for gluing glass to handles on
> the backs of mirrors - -  keeps the warmth of your hands away from the glass
> - - - sorry for the guys with the twenty inchers though because to remove it
> you put it in the freezer overnight and a smart sideways smack with a piece
> of two by four and it falls off. We use it a lot for edging small lenses, it
> takes a lot of punishment at room temperature. I have used it to center and
> edge six inch refractors at low (10) rpm. The glass must be well cleaned. It
> is getting hard to find at any but the old established stationers

My belief is that sealing wax consists of shellac, possibly softened
with a gum of some kind, and a pigment.  I am uncertain about the
softener, even if it be necessary.  Gum Sandarac is probably suitable,
but is hard to find.  Gum Mastic might work, and is available at
Middle Eastern groceries, as it is used in Turkish cookery and as
a chewing gum. (mastic, masticate,...)  Red rouge might make a suitable
(non-abrasive) pigment or lampblack.  Pigment may not be (is not?) needed.

Solid (flake) shellac is still an active item of commerce and is
available at around US$10/lb, depending on grade.  www.shellac.net
is one of many sources.  It is a tractable substance to handle, and
can be melted and cast into sticks, or even formed with the hands
in a somewhat dangerous procedure (due to the cabinet maker Tage
Frid).  Orange shellac that has not been dewaxed is probably best
for this.

Take an iron plate about 1ft square, place a quantity of shellac
flake on it.  Wet down the flakes with alcohol and ignite.  When
the shellac is melted, thoroughly and liberally annoint the hands
with 30 wt motor oil, blow out the fire, and shape the molten shellac
into rough sticks, like tootsie rolls, or such as what the cat is
wont to bury.  A nasty burn results if you don't oil your hands.
The resulting tootsie roll is called "shellac stick" and is used
molten to fill furniture dings.  It is also sold as "shellac stick"
at woodworking stores, and again is said to be sealing wax, except
pigmented to match wood colors.

I've done this twice without being burnt; the young or the squeamish
might substitute some sort of putty-knife-like tool dipped in oil.

Shellac stick whether bought or made lacks the wicks seen in some
sealing wax.  It is usually melted with a hot spatula in woodworking,
but can be ignited or softened with a alcohol lamp or Bunsen flame.

Dave

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