Sandy King (sanking@hubcap.clemson.edu)
Thu, 03 Jun 1999 15:04:05 -0400
As far as I can determine there are no benfits to using deionized ossein
over a porcine skin gelatin like Knox unflavored food gelatin for carbon
printing. I have used them both with good results. In any event, you can
actually buy both types of gelatin from Kind and Knox in large quantities,
bone (ossein)and porcine skin.
In response to a previous question about the relationship between bloom and
sensitivity, I think there is none. However, since viscosity must also be
taken into account (since this significantly affects how fast and at what
temperature a carbon print clears on warm water development) the question
,is a little more complicated than at first glance. Still, as I have said
before it is primarily the strength of the dichromate sensitzer that
determines sensitivity in colloid printing, not the type or strength of the
colloid, be it gum, fish blue, albumen, or gelatin. Although some of the
gum printers don't buy this it is clearly demonstrable with a little
careful testing.
Of course, if you are actually using the gelatin to coat carbon tissue the
bloom has to be carefully considered with relation to the temperature of
the room where you will coat. A 10% gelation solution made from a mid to
high bloom gelatin (175-300) will set at a given temperature much more
rapidly than a 10% solution made from a 100 bloom gelatin. But if you
dilute the mid to high bloom gelatin to a 6-8% solution it will behave
essentially the same as the 100 bloom gelatin at 10% solution.
Sandy King
>On Thu, 3 Jun 1999, Wayde Allen wrote:
>
>> On Wed, 2 Jun 1999, Mac Legrandi wrote:
>>
>> > What are the benefits of using Deionized Ossein over Knox gelatin for
>> > Carbon printing or any of the gelatin processes?
>>
>> First of all, ossein isn't exactly gelatin. It is the organic residue
>> (primarilly collagen) left after the mineral content of the bone is
>> dissolved away, and is the precursor to bone gelatin. Ossein requires
>> further treatment to convert it to gelatin.
>>
>> I don't know if there are any particular benefits. I would guess that
>> there aren't any and would be partial to the use of Knox gelatin for
>> carbon printing, but then I've been wrong before.
>>
>> > Is it worth buying?
>>
>> I'm not certain. I guess it depends on the cost, and if you want to
>> experiment.
>>
>> Terry King was the guy who was pushing the use of deionized ossein for
>> paper sizing. He claimed that it worked great and required no chemical
>> hardening. You might want to take a look at the list archives to see what
>> has been said about it. I personally have no experience with the stuff.
>>
>
>As is in the archives, presumably, I was unable to get a size of deonized
>ossein to do continuous tone gum. It may have for a couple of folks, but
>not here -- with or without hardening. Nor did it wash off cleanly where
>it did clear, but left in blotches. It apparently cleared with brushing,
>but there still didn't seem any advantage to using it (except the fancy
>name).
>
>Judy
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