Re: Gum hardening -- top down?

Terry & all,

the idea that a bunch of "free" molecules could aggreate in bundles or in layers without somekind of force acting on them goes against the laws of nature. If there was some (chemical) force attracting the dichomate molecules at the paper surface, which is not impossible per say, this would mean the paper could also attract other kinds of molecules and this would inevitably cause the paper to degrade at a much faster rate then what is currently observed. In other words the paper would be unsuitable for practically all types of process.

Some may think gravity could cause the dichromate molecules to sink until they meat the paper and aggregate there but this is also impossible in this context. A good example of this is the air we all depend on, the concentration of molecules of air is for all practical purpose exactly the same anywhere in the room. Before you tell me that at the atmospheric level this isn't true which is exact I'll add that gravity is a very weak force and in a room it is basically annuled by the presence of heat (energy) which impart a significant mouvement to the molecules of air which make it quasily impossible that they will ever aggreate anywhere in the room. The same principles and physical laws apply for liquids and solids at different degrees of course.

The only force that is significant enough to make the molecules gather on the surface of the paper would be chemical and as I already mentioned above the paper you all currently use have been design to be neutral chemically. In other words, by design, the paper you all used today don't have enough chemical potential energy to attract molecules at there surface or within them.

I understand that adding chemicals, water, dichomate, gelatin, gum and what ever else will inevitably change the properties of the paper especially it's chemical neutrality. If this change in neutrality is significant enough that it causes some molecules to become "attractors" and force dichromate molecules to aggregate at its surface and bound with the paper molecules well I'm no chemist but I know that humidity and contaminants are always present in the air and the paper should be relatively immune to this kind of attack by design which make me believe that it should also be immune to dichromate as well. Is this actually a fact, I don't know but if it is possible that dichromate molecules compromise the papers chemical neutrality then I'm sure there are plenty of other chemical present out there to do just the same and the paper surface would become coated with them in a blink of an eye sort of speak. Our images wouldn't last very long and it would be a short time, just enough for a contaminant even of very low concentration to buildup to make it visible and bye bye image.

Regards
Yves

  ----- Original Message -----
  From: TERRYAKING@aol.com
  To: alt-photo-process-L@usask.ca
  Sent: Wednesday, April 05, 2006 10:40 AM
  Subject: Re: Gum hardening -- top down?

  The difficulty with many of Mike's 'speculations' or assertions is that one simple test will disprove them. Try, for example what happens if you make a platinum print with a 1.2. or 3% gelatine size.. No precipitation and no need for Tween or special papers not sized with gelatine.

  Anyone making carbon prints or gum prints will have conducted this test every time they make a print. Experience is that the gum or gelatine hardens from the top. That is why too short an exposure leads to the picture sliding off the page; the gum has not hardened at the surface of the paper..

  Stopping to think for one moment will demonstrate the truth of this. Sandy has amply made the point by demonstrating that the gum hardens at the paper surface when it is exposed from the back.

  Terry

  In a message dated 5/4/06 3:07:13 pm, kthayer@pacifier.com writes:

    In the past, the "proof" that has been offered here for hardening at
    the paper surface is no proof at all but Mike Ware's speculation that
    the dichromate may be strongly absorbed to the paper; he thinks it
    may move down through the layer and congregate at the paper
    surface, and if this is so, that is where hardening would take
    place, because that is where the bulk of the dichromate would be
    found.
Received on Wed Apr 5 11:16:34 2006