Re: possible answer to archivalness comparison between carbon gum andpt/pd
Shadow values of 2mm above the substrate is awfully high. I have never seen a carbon print with anywhere near that much relief. My own prints, even with my high relief tissue, tend to have no more than about .2mm of shadow relief over the substrate. But even this amount can be rather spectacular on some substrates.
The B&S commercial carbon tissue is not very thick. It is hard to measure the exact value but I would estimate that shadow value over substrate is about 0.04mm.
At 2:36 AM -0500 3/2/08, etienne garbaux wrote:
Sandy wrote:I am currently making a very thick carbon tissue (weight height of about 1mm) for negatives with a log density range of about 2.7. With the correct sensitizerSome of the 19th century examples I have, and others of that era I have seen, have deepest shadows around 0.075" (nearly 2 mm) above the substrate. Around 0.035" to 0.050" seems more typical in that era, and some are only 0.020" or 0.030". The alt-carbon prints I've seen in the last 15 years or so appear to have less than 0.010" of relief, but I haven't been in a position to measure one accurately. Some commercial tissue I was shown recently looked to have less than 0.020" of gelatin (again, eyeballed, not measured).