[photo-3d] Re: heat seal vs spicer vs RBT, now vs alum/glass!

[<donaldparks@xxxxxxxxxx>]

> Bob wrote:
> Hey ..... at least we can still get SOME kind of stereo slide mount.
> Thank goodness we are not discussing the best materials to make our own
> mounts from, because stereo mounts completely disappeared.

    Thanks to Paul I'm now in business mounting my horizontal half frame stereo pairs in heat seal mounts.

    Formerly I took all my slides with a Realist and mounted the 5p films in Realist aluminum masks putting the best ones in
glass for projection.  IMO stereo slides do look better when they are mounted in the always sharp and perfectly opaque aluminum
masks and the glass provides protection as well as more consistent focus during projection.  I never used heat seal mounts
since, in those days, Kodak did a pretty good mounting job and it was easier to have them do it for the rolls I was too lazy to
mount myself.

     I once took a tour (about 40 years ago) of the Kodak slide processing center in Chicago and asked to see how they did the
stereo mounting. As I recall, there were several, fairly large semi-automatic machines with a place for an operator to sit at
each machine.  The mounts they used were uniformly coated cardboard heat seal mounts that didn't have any film alignment tabs.
The machine advanced the film automatically once the operator had started a roll and set it to cut the film at the start of the
first image.  After that he or she only had to check to be sure the roll didn't contain any places where the film improperly
advanced in the camera.  The machine cut each film chip and placed it in the right order on a mount automatically.  It must
have used a way of heat tacking the film chip down to the mount.  There was no tape.  After both chips were on a particular
mount the machine folded it, heat sealed it, punched a date on the face and fed the finished mount into a bin or box in the
right order.  The precision of the mounting was at least consistent.  If one slide was out of vertical alignment they'd all be
out of alignment by the same amount.  The stereo window for all slides was set a 7 feet.  Anything nearer than 7 feet appeared
in front of the window and so on.  The slides were mounted correctly for viewing the scene through the smaller cardboard
aperture which produces a fairly sharp looking stereo window.

    I've had a couple of rolls mounted by Kodak recently and have taken apart some of the mounts.  It looks like they do it all
manually using uniformly coated heat seal mounts that have tabs to help the person doing the mounting place the film chips.
Transparent tape is used to hold the chips down before the mount gets folded and finally heat sealed.  If the mounting
technician is not very skilled or not paying attention the mounting job can be pretty poor with major mounting errors.  They
probably don't bother to take the curl out of the film.  When the film has a curl you have to place the film chips curl side up
to effectively use the mounting tabs.  This makes the slides come out backwards, meaning that the slides need to be viewed
through the larger cardboard aperture and have an annoying lack of sharp definition to the stereo window.

>Linda asked -
>So, folks, do you pretape or not??? Enquiring minds want to know, as do
>developers of new heat seal mounts.

    I like mounts that hold the film chips securely but also allow continuous adjustment for setting vertical alignment and for
the horizontal movement that sets the stereo window.  The old Realist aluminum masks did these things.  Once the film chips
were inserted into the tracks they would stay put but you could slide them a little bit vertically and quite a bit horizontally
to achieve the best alignment.  You could adjust the chips little by little, viewing the slide and checking spacing with a
mounting guide multiple times.  After you were happy with the alignment of the chips, the plastic mounting tool was designed to
crease the aluminum fold and make the chip positions more permanent before taping the aluminum mount between sheets of glass.
RBT mounts do this even better.  They are a little expensive so some people us a trimmed RBT mount for setting the film
alignment and then transferring the aligned films for final taping to a cardboard Spicer mount.  David Kesner has this
technique mastered.

     On the current type of heat seal mounts you have to use some way to secure the film chips to the mount.  The method might
include using tape, a hot soldering iron or a hot glue gun tip to attach the sprocket edges of the films to the heat seal
coated surface.  This way of putting the films on or in the mount does not allow continuous readjustment.  Once the chips are
taped to the mount any further horizontal or vertical adjustments would require untaping and then retaping.  IMO it would be
much harder to end up with a well mounted slide using these heat seal mounts.  Also, the final heat sealing takes some skill
too avoid touching a hot iron to the film chips.

    The heat seal mounts I use for my horizontal half frame slides are made using a heat seal layer that is cut out where the
films fit onto the cardboard mount.  They are like the mount samples that Paul Talbot gave out at the Mesa NSA. The area where
the film chip sits does not have a heat seal coating on it.  However, my mounts are designed with a slight difference.  They
have heat seal around only 3 sides of the film chip.  The thin strip at the edge of the mount is missing.

    The mounting method I use involves carefully heat sealing the mount closed before I put any film chips into the mount.
This can be done rapidly without having to be careful about heat damaging films since there are none in the mount.  I am
careful, however, not to compress the non-heat seal film pockets.  Then I slide the film chips into these pockets in the mount
from the edge where the heat seal was missing.  The mount holds the film chips securely and I can preview the slide to see if
it's worth adjusting the alignment of the film chips any further.  If I don't like the slide I can simply slide the film chips
back out and reuse the mount.  I may leave a roll or two mounted this way awaiting a final viewing to decide which slides to
keep.  The ones I decide to keep need to have the films carefully aligned and secured more permanently.  To do this I slide the
film chips partially out of the mount and put a thin piece of double stick tape (acid free and hopefully archival) on the
sprocket area.  Then I carefully slide the chips back into the mount.  If I avoid compressing the mount the films will still
slide horizontally and vertically to allow continuous precision adjustment.  I check and adjust the vertical, rotational and
stereo window repeatedly (on a light table, in hand viewer or even in a projector) until I'm happy that the slide is in correct
alignment.  Then I simply compress the mount areas over the double stick tape to set it's adhesive and hold the film position
permanently.

    So my answer to Linda's question is double stick.  -  Don Parks