Re: Standard formula

At 02:10 PM 12/26/2001 -0500, you wrote:
>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!

But if my observation is correct, a big but, glycerine counteracts this
tendency.

>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.

Increasing of contrast is an issue still in contention with me. It doesn't
seem to be the case but again, only my cursory observation at this point.
It does, however, seem to raise the set point. I juiced up a batch pretty
heavy with it something like 150 mls per 2000 ml of coating and it was a
drippy mess coming off the machine where the same mix in a lower
concentration did not.

When you read historic literature telling you to filter the glycerine
through cheesecloth to remove the floating crap out of it one can only
imagine what the stuff must have been like. I suspect it may have been some
kind of rendering from slaughter houses done in the back shed! It is
entirely possible that glycerine in the olden days was full of reduction
components or oxidizing ones which may have been the culprit. Today it is
crystal clear. Who knows?

>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.

Very much so!

--Dick

>Sandy King
>
>
>
>
>
>
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>>
>>
>>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
>>_______________________________________________
>>Carbon mailing list - Carbon@opusis.com
>>http://rmp.opusis.com/mailman/listinfo/carbon
>
>
>--
>
>_______________________________________________
>Carbon mailing list - Carbon@opusis.com
>http://rmp.opusis.com/mailman/listinfo/carbon
Received on Wed Dec 26 12:41:15 2001