Re: Standard formula

Kemal,

>
>Shouldn´t we write down a standard carbon tissue formula and put it on
>carbon@opusis site?

I believe you can find numerous standard carbon tissue formulas on
the carbon resources web site. Most, though not all, of the old
formulas are stated in terms of 1000ml of pigmented gelatin solution
and that is how I have elected to state my own formulas. This may not
be a theoretically perfect way to state the formulas but it is
consistent with historical literature and simple to explain and
understand.

>I know
>also that some of list members hold carbon workshops, but revealing
>their "secrets" should only increase interest in carbon.

Well, I conduct workshops but am not trying to hide any secrets.
However, bear in mind that there is no one magical formula as the
process will work with considerable variation in the quantity and
type of ingredient and in the actual working practices of good carbon
printers. Moreover, some of us are constantly experimenting to find
ways to achieve certain ends. For what it is worth, I would consider
the following a fairly standard formula that should work well in most
circumstances.

        Water 1000ml
        Gelatin (175-250 Bloom) 100g (porcine or ossein)
        Sugar 30g
        Glycerine 25g
        Pigment (Sumi Ink or like) 30g

Use about 50ml of this solution to coat an 8X10" tissue, 100 for a
11X14" tissue. Coat at room temperature at about 70F with the
pigmented gelatin solution at around 90-95F. You should not need a
frame to contain the solution in these circumstances so just pour the
required amount of solution into the center of the tissue support and
smooth to the edges with your fingers, a comb, or a rod.

Variations are possible as follows.

Gelatin - Use a slightly lower percentage if room temperature is
below 65f, higher percentage if room temperature is above 75F.

Sugar - Some of this organic material is needed to make the process
work and to give pliancy to the tissue. Too much makes the tissue
brittle!

Glycerine - In small quantities even more effective than sugar in
giving pliancy to the tissue. However, in very large amounts
increases contrast of tissue. May be omitted in areas of high
humidity but very useful in the winter and in areas of low humidity.

Pigment - More pigment gives tissue of higher contrast, less tissue
of lower contrast. For tissue that give images of maximum relief
double of triple the amount of coating solution for a given tissue
size over the standard formula above, using only 1/2 of 1/3 of the
standard amount of pigment per 1000ml.

Hope this information is useful.

Sandy King

>
>
>I would sugest a formula like this:
>
>Gelatin 100%
>Sugar 30%
>Glycerin 25%
>Pigment
>10% Thymol
>
>For people who like ready served formulas we should write the formulas
>in 8%, 10% and 15% gelatin solution. Then we shoud explain an influence
>of gelatin concentration, Bloom, sugar-, glycerine- and, very important,
>pigment concentration.
>
>Kemal
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>Carbon mailing list - Carbon@opusis.com
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