Cementing glueing prism
per.c...@privat.dk
when the chance are there, recently I experienced a problem I hope
someone can advise. Some prisms are glued together by two prisms, but
with two of the binucular I found the glue from round 1920 loosened
and I find it very difficult to find a glue to repair the prisms.
The binocular I mention are Moller Wedel brand but beside the two
Tourox in question, I am also talking about the same foult, -- that a
small 90 deg glued on prism falen off, from a Frensh "Stereor Paris"
flat binocular with same Moeller rooftop prism, -- thought moeller
wedel was the only to use this particular prism, but no these Stereor
carry them to. But all of these are build from two prisms
http://www.monocular.info/moellerp.htm, and that is where my problem
are ; how to blue these two pieces of glass back together ?
Bob May
the Canadian Balsam tree purified. You should be able to buy this still
from large optical supply places in stick or liquid form. Zylene is usually
used to liquify the stuff for application. You may be able to get it to
"glue" back together again just by the light application of some Zylene to
the joint and let it sit for a while.
Normally the application of the Canada Balsam is by putting a dot in the
middle of the joint desired and slowly putting the two parts together making
sure that there are no bubbles produced by the process. The Canada Balsam
is usually thinned to the point of where it acts like ordinary paint.
Good Luck.
--
Bob May
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Richard J Kinch
> But all of these are build from two prisms
> http://www.monocular.info/moellerp.htm, and that is where my problem
> are ; how to blue these two pieces of glass back together ?
UV cured cement from Edmund Optics. (You will find a UV cured optical
cement hidden at your local auto parts store as a windshield repair kit.)
For one job you can use the midday sun on a clear day as a UV curing lamp.
Canada balsam from surplusshed.com.
Richard J Kinch
> You should be able to buy this still
> from large optical supply places in stick or liquid form. Zylene is
> usually used to liquify the stuff for application.
They offer it at surplusshed.com but I have not sampled it for quality.
I suspect you mean "xylene". Just about any nonpolar solvent will work,
like naphtha (Coleman fuel) or mineral spirits. But my understanding is
that balsam cement was applied with heat, not solvent, although solvents
were used for uncementing. A solvated cement would take forever to set,
because the layer is very thin and trapped between glass. The technique
was obsolete by WWII.
P.C.
Thank you -- I tried with shellac, and the first tests with a drop on
a glass surface, showed it was difficult even to scrape away and had
to be soluted to be removed. But between two pieces of glass the
alchohol wil not fume away and only the edges, so my first test about
ahellac's ability to stick to glass showed it to be unusable, ---
that's why I wonder what was used as I offcaurse would use that again
if possible, Othervise I will look into the UV hardening Epoxies, I
has an 250 watt UV lamp, case that is the type of UV these epoxies
ask.
Here one of the two Moeller-Wedel binocular with this problem ;
http://img269.imageshack.us/img269/6552/moellerwedel.jpg
Thank's
P.C.
surprised me is offcaurse that I read that these prisms was used by
Moeller Weden, but cleaning these binocular that I can find no
informations about on the web, I found they use the exact same roof
prism with an on.glued small prism, exact same design as Moeller Wedel
1920's design that later was taken over by Zeiss .
Here the frensh binoculars ;
Bob May
inline and the offset design. Probably the biggest difference in binocular
design is in the actual prescription of the objective lenses.
I'll nte that the original method of gluing glass together was the Canada
Balsam but if you are not interested in doing a perfect "restore" of the
binocs, the UV cements are a lot better choice as it is a lot easier to do
things that way. Do make sure that you have the prisms in exactly the right
place or the binocs will not put the two exit pupils in the right place.
There are adjustments that can take out a lof ot that error but theere are
limist as to how far you can move them.
P.C.
Thank's Bob, -- As I read your answer, I can use an Epoxy and if I
make a foult then nothing can be done about it. With the old fasion
way on the other hand, there are a way to solvent the glue case I make
a foult. But another problem "Canada Balsam " I wonder where to find
that in Denmark ;))
Joe
<per.c...@privat.dk> wrote:
>
>Thank's Bob, -- As I read your answer, I can use an Epoxy and if I
>make a foult then nothing can be done about it. With the old fasion
>way on the other hand, there are a way to solvent the glue case I make
>a foult. But another problem "Canada Balsam " I wonder where to find
>that in Denmark ;))
Canada Balsam was a very popular cement used in the preparation of
microscope slides. You might want to ask at universities and older
microscope dealers. It is not used much anymore, but perhaps some
department or company has some old stock remaining.
Good luck.
Joe
Phil Hobbs
If you use UV epoxy, you can tack it (i.e. cure the centre just enough
to hold) and still get it apart if it's wrong.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
P.C.
wrote:
I guess it will be a handyman's repair -- I can make some tests first
with the UV lamp, but that is only an UV lamp and not a particular
tool, so I wonder if I can maneage a profesional attitude. The Balsam
issue is interesting. As I told I tried Shellac soluted in spirit and
on open surfaces it is just perfect as varnish, but between two pieces
I doubt it's value for several resons and in particular becaurse it
will be years before the final spirit vapored away leaving proberly
air bubbles.
Xylen I think it is spelled ---- funny but I was a bit surprised
searching using the name Zylene --- go I gues as the spirit, but
proberly in smaller quantity to solute just enough remind me of the
natural resins and I wonder if not this resin had other porpus so it
will be able to be found, gee -- it's that small quantity, and even it
profesionaly done now proven it's limits, then I would be most happy
to do a repair to last 70 years as what seem to be the limit for this
cementing.
Thank's everyone !
anorton
http://shop.ebay.com/merchant/qcprospector
I would agree with others that the modern UV-cured cements are much easier
to work with and probably longer lasting. I would only use the balsam if you
want to restore it with historical accuracy.
If you do use balsam, the prisms must be clamped carefully so they do not
move when curing in the oven, but the clamps should not put too much strain
on the glass either. The balsam becomes much less viscous when it first
heats up and the two pieces of glass tend to shift. You might need to
improvise a special fixture to do this.
--
Adam Norton
Norton Engineered Optics
www.nortonoptics.com
(Remove antispam feature before replying)
P.C.
Thank's. --- Exactly that issue a jig to hold the pieces in place and
you say, "an oven".... made the decision easier, -- they are small, no
face are vertical or horisontal, there are no way to clamp the small
one as it is triangled , --- well these thisgs has to be done anyway,
but there be a difference of one to move an a jig that only need to
situate the pieces for a moment.
Bob May
you do the job right, you can easily remove the jig, put in the cementing
material, put the jig back on and put it into the oven. Also, you can have
a bit of a time where you can test and align the prisms perfectlyl in the
binocs. Dental stone, for example, has a working time of a good 10 minutes
and will be hard enough to handle in 1/2 hour if you are gentle with it.