Index matching

Anyone have any foolproof methods for index matching sheets of PFG-01 roll film to glass? For 4×5" sheets I’d used both mineral oil and lamp oil with decent success, although I detest the messiness of it.

I’ve been working on the final Minas Tirith hologram and the last sticking point (as it were) was getting a 5×7" hologram done using 5% TEA solution. For lesser concentrations of TEA I was quite happy with sandwiching the film between two pieces of glass and shooting at ~56 degree angle.

Unfortnately at 5% I couldn’t get a fully dry piece of film no matter what I tried. Even a final hair-dryer treatment didn’t help and the film would stick to the glass and shift during the exposure, resulting in ugly black blobs. A sure sign of film movement.

I tried a couple of mineral oil matched shots last week and couldn’t avoid some movement even with 30-45 minute settling times. This really sucks because I’m burning 5×7" film every time, as well as burning a few hours every morning with nothing good to show.

Yesterday morning I tried lamp oil and had better results after just a 30 minute settle but the image was off-center enough that I decided to try another shot in the evening (these days I only have time for one attempt in the morning). Unfortunately the evening shot moved. Perhaps I wasn’t careful enough when applying the film or rolling out the fluid. I’m not entirely sure though. It could also be that for the morning shot I was using freshly TEA treated film which had been relaxed by the soak and hadn’t re-curled fully to its original shape. In other words, it was flatter than normal. On the other hand, the second piece was just as curvy as usual and perhaps this was causing more tension.

This morning I soaked another two pieces of film, left one to dry and blow-dried the second. I taped down one end of the film (emulsion side up), applied tape to the sides, put about 1ml of lamp oil on the plate at the first end and used a brayer roller to squish the film down and force the oil out the other end. Because of the tape on the sides, the film was held down after the roller passed and I only needed to give the tape a going over with my finger to make sure it was adhering to the glass. I then put another strip of tape down to hold other end of the film to the glass. I let this settle for 40 minutes and ended up with a bright clean hologram. This one’s a keeper and will go to its new owner on Monday.

Sometime this weekend I’m going to try the second piece of film and see if I can refine my methods. I can see a few potential problem areas:

1) Maybe I’m not allowing enough settling time at 30 minutes.
2) Maybe I’m not squeezing enough of the oil out, causing number 1.
3) On this morning’s shot I noticed some small dust grains between the film and glass. It may be that this is happening more often than I think and that those grains are causing cappillary action and long-term movement of the oil. I need to switch from using paper towels to clean the glass and clean both the film and glass with some kind of lint-free cloth before index matching.
4) I will definitely need to refine my application methods. If the film is curling on the long axis, perhaps I could leave out the side tape and squeeze out the oil with a squeegee, tape down the second end, clean up the oil and then tape down the sides. This might allow me to get more oil out and provide a tighter bond.

If anyone has any recommendations for this combination of 5×7" PFG-01 (roll) film and index matching, I’m all ears.