Carbon Transfer: anyone try Calvin's 'supercoat' tissue concept?

[koraks]

How thick is the gelatin of a typical highlight relative to the thickness of the supercoat

By nature of the carbon transfer process, this question cannot have a discrete answer. But perhaps this is what you mean: if we assume that the tonal threshold fairly consistently occurs at a certain film thickness, the supercoat would have to be slightly thicker than this, but not much more. In this balancing act, erring to the thicker side would be safest. I assume that Calvin's testing has led him to determine a suitable thickness for the supercoat. He coats it to a wet height of 0.5mm, but since the gelatin load is very low (<1%), the dry film size may be something in the order of magnitude of 5-10um. I couldn't say at what specific wet film thickness the tonal threshold typically occurs. I don't even know how fixed this figure is; I have a feeling it might be a fairly narrow bandwidth assuming the process and materials are reasonably tuned.

but so glad I am not going in that direction

It's a choice. Mind you, there are other ways of optimizing highlight rendition with DAS carbon and continuous tone negatives. I find Calvin's approach interesting because I suspect it may be superior, and it's certainly fairly flexible. And I'm of course thankful for Calvin taking an issue seriously that has been downright denied by some of the carbon transfer experts, to my disappointment.

 

[Vaughn]

It was sort of a rhetorical question -- just highlighting the significance of the relatively thin supercoat to the thickness of the gelatin in the highlights.

You should have been around (maybe you were) for the old carbon list-serve Sandy King maintained in the 90s. We were constantly re-inventing the wheel, coming up with reasons why something worked or why it didn't. Someone's idea would get shot down, only to re-emerge later as accepted fact...or the other way round. A lot of exploration on the traditional carbon methods of the times.

But the supercoating is a wonder. Why would a clear layer smooth out the transitions between tones in the upper values relative to no layer, as he suggests? Pretty neat, but a wonder.