Michael, nice to hear from you. Here are the answers:
>1. Are there advantages in using Gloy rather than standard gum ? Is Gloy archival ?
Terry: It is more consistent; it does not go off; it is faster; it will accept controls more readily. I am not aware of any testing but I can see no reason why it should not be archival, but I suppose if one were concerned for the centuries ahead, and one wished for greater certainty, one would stick to gum.
>2. Which sizing method is best? Has anyone tried polymers etc.? As gelatin (even hardened gelatin) is hygroscopic would there be registration problems on large prints due to water absorption ? Is it possible to size with gum (or Gloy) + dichro. + UV instead of gelatin? Is sizing necessary in between each gum layer ?
Terry: With standard water-colours I use a gelatine coat between layers. As an aid to registration a coat of acrylic or Gloy, dichromated and exposed, as a size helps or the paper can be stretched first. Using heavy sheets of glass and heavy estar based films, I find I have little trouble with registration whatever the method.
>3. How large can a gum print be using normal coating methods (20x24 inches) ?
Terry: What is normal ? I know someone who makes gum prints of people twice life size using a garden brush to coat the paper.!!!
>4. Which brushes are best for the coating process? Are other coating methods better ?
Terry: I find water-colour laquer brushes best. Hake brushes are good if the 'emulsion' is not too glutinous.
>5. Is it better to use a less concentrated form of the ammonium dichromate to avoid staining ?
Terry: Dichromate does not stain if it is not over-exposed (when it turns green). If you expose just enough to harden the highlights a good wash clears away the dichromate.
>6. Can hot water spray development be used with gelatin size or would it dissolve again ?
Terry: It should not as it has been hardened by the dichromate unless the pigment is so thick that the light could not get to the gelatin.
>7. Is there a reliable table of gum/dichro:pigment proportions for eg W&N pigments which might guide me ?
Terry: Just keep to 50/50 gum/dichomate. The tables that some suggest are pointless complications. The pigment is not the factor; it is the opacity that counts.
>8. I have tried 1/2 Hr automatic development and got an inadequate image - is spray dev. better? Hot water? Forced jets?
Terry: I use brushes, hoses, sponges, kitchen scourers. I would not use automatic development as one would get a better picture by going to Snappy-Snaps ! Half an hour sounds far too long.
>9. Can smoother papers with less tooth work with gum, eg Fabriano-5, instead of BFK or Bockingford ?
Terry: I started with Bockingford and kept with it for years. Now I use Fabriano Artistico hot pressed for nearly everything.
>Sorry to bore you with my trivia - it is too naïve to place on the main alt-photo list!
Terry: Not trivia at all. This is the sort of thing that is grist to the list's mill. I would be happy if you were to copy it to the list.
These are the sort of questions that someone with an understanding of the problems asks. Answers and methods are likely to differ from person to person. Intelligent discussion and practice in a workshop environment is often the best way of resolving these issues. We are running a series of weekend workshops in Richmond. There is one at the end of this month. Would you be interested ?
Terry