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Re: phosphors
Dear John,
There are mainly three different binders for fluorescent powders, namely the
binder for the sponge technique, the glass-beads technique and the liquid
technique we call the PHILIPS suspencion technique.
We never use the technique here in Europe that you tried out, infact I don't
even know how it works. We call that the cold cote no bake technique, so using
this technique it's not neccessary to have an oven. But it's just the use of a
bake- or annealing oven which make the neontube superior to other tecnique's.
Even when we use pre-coated tubes we still bake the tubes out for making them
more clean and hydro free. What you actially do is sinter the fluorescent layer
to the glasswall (again) especially important where the tube is bend. Anneled
glass is three times stronger then before, so speaking about quality every
bender must consider the use of an oven. I am convinced of the fact that this
procedure is not more costly because there are less failures or thermal breakage
(from the thermal tension in the bend) then not using an oven. The lifetime of
your pump-medium is more then doubled and the pollution of your manifold is
minimized. Doing merc repairs is vey easy when you bake out the glass first. All
block out paint is vanished from the glass and the merc is sucked out from the
tubing out of the closed oven by a fan when the temp is about 350 C. The exhaust
merc polluted air is simply lead through a waterbed so that there is no merc
vapour in the environment. Afterwords (when is neough merc) the merc can be
triple distilled under vacuum and used again. That triple distilled is not a big
deal. The unit you need for that is very simple to build from a roughing pump
and a diffusion pump. I have blue prints of such an installation, so if you
think that it is interested to you I can post them. It's realy an easy to handel
operation to distil old merc, saving money and it's god for the environment.
Back to binders.
The binder for the sponge technique has a strength of 4 to 5 % and for the
glass-beads technique a strenght of 3 %.
The binder is never made with a component like camphor in it, we us ethat for
other purposes. The binder is made from Aceton, spiritus Phortior and a glue
like Phosphorus Pentoxide like P2O5. Make sure that the aceton (and all the
ingredients) are chemical pure. Never use the cheap technical pure solvents.
The solution for making a liquid suspencion is different from the dry powder
binder. This solution is made from Spritus Phortior, Amelis Acetas and a
nitro-cellulose in a specific concentration. Selling this solution through
Western Europe you must forgive me not to publish the exact percentage's of the
different ingredients. Preparing a liquid suspencion you must mill the dry
powder in a milling vessel with ceramic balls inside for about 24 hours with 110
RPM. So the vessel must do 110 RPM and not the machine. Using thing bars (like 5
cm) the bars must do about 750 RPM. The ceramic balls have a diameter of 15, 20
and 25 mm and the vessel must be filled halve with balls. When you have a powder
with a specific gravity of 1 you can make halve a litre of suspencion from halve
a (European) pound of dry powder. The viscosity of the liquid must be about 10
or 11 Zahn seconds for the powdering bend tubes, and the viscosity mmust be
about 17 Zahn seconds for straight tubes before bending. So for Brilliant Blue
you can make 550 ml with 250 grams dry powder and for standard blue there is
only 390 ml suspencion. The reason for that lies in the fact that standard blue
has nearly (whatever the brand is) a specific gravity of 2 and BB is lighter
then 1.
All nitro-cellulose is vapourising at 350 C so at that temperature there is a
build in fan in the oven sucking out the NC vapour with a hysteresis of about 3
minutes. Then the tempearure is rising again to the annealing point. For us only
using soda-lime it is 480 C so just under the aneealing point to prevent that
the glass wil have other curves then before. These temperatures are continued
with a hysteresis of about 5 minutes. The cool down period of neon tubing is 1 C
m E -1. Following this procedure your glass is completely annealed and therefore
3 times stronger. All ovens are heated by electrical power. We never use other
sources any longer as these are old fashioned and unreliable. Men can regulate
electricity so perfect with a narrow band of hysteresis that other sources or
procedures are inferior compared with this one. The dimensions of an oven are
mainly 3 mtr long 1 mtr wide and 1 mtr height. The installed power is then about
14 kVA or as you say 14 kW. The maximum capacity of an oven is about 40 to 50
pieces of tubing to heat in one time., so all neonshop are using the oven every
day and are heating up overnight (nite?) when the cost of electricity is halve
price. Your puming procedure and pumping time is shorter when the glass is oven
annealed and baked and your manifold will stay cleaner for month. So please
consider the use of an oven. Your work will be more brighter with a much higher
light output and stay longer in the right original colour than before.
Hope that this is enough fuel on the fire, like you asked me,
is signing with best regards
dirk a. boonstra.
PS: John if you think that it will be a help for me that you correct my letter
in proper English, please do. But don't put it on the list, so mail it direct to
my adress.