I probably will be sorry for opening my big mouth, but I should think altering the development time would affect Polaroid Type 55 about the same as development of traditional film. I remember that the negative requires a little more exposure than the print. I have a pack in the frige so I'm anxious to hear your results.
The Type 55 developer is a monobath-type gunk, so changing the time won't do much difference to the negative. But you CAN strip it (undeveloped) and develop the neg in your favorite developer...
option 1) Selenium tone the neg. This will add about .2-.3 density in the highlights
or
option 2) bleach and redevelop in a staining developer such as pyrocat or rollo pyro. This will increase the grain somewhat, but if you're contact printing, that really doesn't matter. This would be the best way to get some additional 'effective density'
When I use type 55, place in jug with water & paper towel between each negative - they easily scratch. Then when get home place in hanger & in tank of sodium sulfite for a few minutes, rinse & photoflo. Sodium sulfite isn't something I'd want to carry with me while shooting.
At one of the workshops I was at, a guy had the type 55 with him. After he pulled off the paper he put it in a 4x5 developing take with sodium????to soak for a while. What chemical is that? I want to try out the film, since i have a few packs in the freezer, but forgot to ask here til now.
Sodium Sulfite is one of the most useful chemicals around. It is used as a clearing bath for polariod negative film, as an oxygen scavenger in developers, a main ingredient in hypo clear formula and mainy more.
In small quantities it can be expensive, but in bulk quite cheap. The Looking Glass has it in stock.
I don't think you need it that strong for clearing polaroid film. It seems I threw about a table spoon of it in a 5x7 tray with water and that cleared a half dozen type 55 negs just fine. Photoformulary has it and it is a great chemical to have on hand. Order some Metol and sone Sodium Metaborate and you can make D76H and Split D-23 and of course, hypo clear. I buy it 10lbs at a time.