Did you make any attempt to test sodium dithionite? Although since
suggesting it I was told it's been tried with EDTA for clearing stained
platinum prints and removed some of the paper fillers. This may not,
however, be a problem with a pure cotton paper.
> A series of doubling
>exposures were given to the three substrates in the classic
>photographic manner. with each colloid, in turn. ie
>1+1+2+4+8+16 mins Nine test's in all. The maximum exposure
>being 32 mins.
In that case you'd be better off saying 16+8+4 etc. Because of the
"continuating" reaction in dichromated colloids, the area of the test strip
to be exposed least needs to be exposed last.
>I think one of the most interesting thing to come out of these tests is the
>surprising long tonal scale possible with just dichromate alone,
But as Judy has said you really need to go on to test whether the resulting
image is archival. The oldest pure dichromate image I have has gone from
brown to green and is now very faint.
Philip Jackson