(Editor.... Thanks to Dr. Film for this information.)
No matter what film gauge you're splicing, 8mm, 16mm, 35mm, 70mm, the following information applies. One important exception -----> when cutting 35mm and larger, you must pay attention that you are cutting and splicing the film on the edge of a frame. With 8mm and 16mm, splicing blocks have pin holes for the sprockets and its a no brainer, you place the film in the sprocket hole guides and chop away. However, in 35mm and higher, the frame has at least 4 sprocket holes per frame and if you are not diligent you can easily make your cut through the center of the frame. To make matters worse, the other end of the film could be cut on a different section of the frame and if these two film ends were connected you would have a jump in the framing during the show. You can always tell when some kid put the platter together at your local cinebox because inevitably after the trailers, the feature will start out of frame and you wait till someone goes to the candy counter to tell them to fix it.
Tape or Cement? The answer to that is easy. No matter how large or small your film collection, you'll have to use both. I prefer using cement but I have no choice but to use tape on mylar or estar prints. Cement will not work with those stocks. Additionally, tape can't be beat for emergency use. I keep the tape splicer handy at the projector and rewinds for the quick emergency splices that become necessary during a show. Other than those exceptions, I think cement is the way to go. It stands up over time, runs nice through the projector and will not give out due to cleaning chemicals. Lastly, it's much cheaper. You can make gallons of film cement yourself.... read on.
What kind of tape? The Kodak press tapes are difficult to find, expensive and a bit tricky to install. I would use them only if I had very little tape splicing to do. Otherwise, you'll be happier working with a tape splicer that uses a roll of tape and a cutting device that trims the tape and punches sprocket holes thru the tape in one chop. It will probably cost you about $20 but it's worth it.
Using film cement takes a little practice, but it's not brain surgery. A few practice splices will turn you into a pro. Here's some guide lines... Cut the film with it firmly in the sprocket pegs. Keep the emulsion (dull) side of the film up and scrap off emulsion from the film on the left side of the splicer. All the emulsion should be removed leaving white celluloid base exposed. Wet it with cement and quickly press the other (non scrapped) right side end over the left. Heat is not necessary. A chemical bond occurs rather rapidly.
Film cement is available from dealers. It is not a glue and the word "cement" is really a misnomer. Nothing gets glued or cemented. Rather a chemical bond occurs joining the two celluloid surfaces... which is why it is important to remove the emulsion, so the celluloid surfaces can meld together.
Use fresh cement... it tends to turn yellow with time. Now, as promised, here's how to make gallons of the stuff yourself..... It is little more than "Acetone", readily available at your hardware/paint store. Chop up small chips of clear cellulose film leader into pieces as small as you can get them... put them into a small bottle with Acetone and shake it up. Let the brew age a couple of days and it's ready.
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