Need for sizing

March 17, 2014

rabiephotography asked: hi, thank you for your answer. Just wondering, as most gum processes incorporate gum arabic, potassium dichromate and colours as the basic materials ( I noticed sometimes other additional materials are used) can you please explain the role of gelatine (sizing?) and glyoxal (hardner?) and do you think 4x36W uv units will be enough for exposure (reasonably short)? thanks a lot for your help! •Rabie

Hi Rabie,

Since the Gum Bichromate process can involve coating & developing the paper multiple times (some people do “single coat” gum prints)–it is necessary to pre-shrink the paper before hand.  Doing so removes the sizing of the paper when it was manufactured, therefore the gelatin provides the new sizing and the glyoxal hardens and preserves the sizing.  Check out my post on “Sizing the Paper”.

Regarding using the 4x36W uv units for exposure–it would probably work. You may need to adjust your exposure times.  Using step tablets on the negatives are a helpful guide to determining exposure times.


Leave a Reply