Re: Spinthariscopes, scintillators, etc... (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 12 Nov 2003 18:09:12 -0700
From: Kevin Christiansen <kevinc@xxxxxxxxxxxxxxxxx>
To: hvlist@xxxxxxxxxx
Subject: Re: Spinthariscopes, scintillators, etc...


Hello again!

I just wanted to send a quick follow-up on the phosphor
testing that I did a few weeks ago.

Since then, I have broken open two black and white monitors
(a Sanyo and a Pelco) and tried their picture tube phosphors.
They work quite well - better than anything I had tried to
date.  The black and white monitor phosphor is definately
brighter than the color monitor phosphor.

A few days after that, the P-4 phosphor that I ordered from
Richard Hull arrived - a little less than a week after I sent
him my check. Not too bad for a snail-mail round trip from Utah
to Virginia and back.

Richard's phosphor came in a zip-lock baggie inside a zip-lock
baggie inside a nicely padded shipping envelope - complete with
specification sheets on the phosphor, etc.  The baggies contained
5 grams of clean, snow-white, uniform fine powder - much cleaner
and much more even than the junk I have been scraping from the
picture tubes.  Richard is obviously selling brand-new material.
While 5 grams of phosphor does not make a very big pile (about a
teaspoon full???), that's a lot of phosphor. I would probably
need to scrape 25-50 picture tubes to get that much. Ugh!

I quickly made a little spinthariscope screen out of Richard's
P-4 and compared it to the stuff from the black and white monitors.
The first thing I noticed is that my eyes did not take as
long to dark-adjust before I started seeing the scintillations
with the P-4 phosphor.  Richard's P-4 is definately brighter than
anything I have tried so far - probably 50% to 75% brighter
than the B&W monitor phosphors!  Very nice and bright!

So, after spending hours scraping phos out of neon tubes, busting
up cathode ray tubes and carefully scraping off the phosphors while
trying to avoid the razor lead-glass edges, and peering through
a magnifyer in the dark, my conclusion is that I should have started
with Richard's P-4 phosphors in the first place.  They are brigher,
higher quality, non-contaminated, and at 5 grams for $12 (including
shipping), a FAR better use of your time!  :-)

BTW, for those who are interested, here is my scheme for making
a spinthariscope screen out of a 3x5 inch index card.

1) Take a BB-sized glob of RTV and smear it onto the non-lined side
of the card with your finger, moving your finger in a circular motion
to spread it out so that it makes a very thin, very sticky layer on
the card - a circle about 2 inches in diameter.

2) Dump about 1/8 to 1/4 teaspoonfull of phosphor onto the index card
and use a small strip of paper to bulldoze it around until it covers
all of the RTV.

3) Dump all of the excess phosphor off of the 3x5 card onto a sheet
of clean white paper, which can then be folded and used to dump the
excess phos back into the phosphor baggy.  Note that MOST of the phos
will come off as excess.  It takes a vanishingly small amount of phos
to coat a 2 inch circle of RTV.

4) Lay a piece of paper over the phos-coated RTV and press down, to
firmly seat the phos in the (very thin) layer of RTV.

5) Wait an hour for the RTV to dry and you are done!  I used RTV
because it's VERY sticky, it can be easily spread into very thin layers,
and it stays flexible, so that the phos does not flake off when you
bend the screen later.


That's my phosphor experience. If anybody has any questions, etc.
feel free to ask!

- Kevin Christiansen