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Re: [BKARTS] percent solutions? mc, wheat, gelatin



Audrey and Amy,

That's why this is  bookart and not  bookscience :-)
Even were it 'bookscience', the reality is that in all we do, we find
ourselves  ALWAYS in a heuristic situation, (learning, finding out as
we go along) -and even the simplest task entails what chaos theorists
know is that even the simplest system or recipe is 'complex'.  And this
'complexity' extends across many levels, there being a broad spectrum
as to how complex even the complex can be, ranging from the countable
(permutations and variations) to patterns that, like 'pi', are  in a
class with numbers that are called 'transcendental'!
Nothing, I've experienced is 'easily' learned, or known the same way.
It's the "not being able to cross the same stream twice" thing. And
most especially applies in making multiples.  No two batches (editions)
of anything come out ACTUALLY identical. (Certainly not if we do it
ourselves.) Not in My experience. It may well be that it's just me. But
I don't really think so.

Norman Shapiro

PS. I've only just subscribed this past week. This is my first entree
-'lurching around'  reading till now.   More about me later, about my
new web page which I'll be launching very soon.


On Mar 18, 2005, at 7:45 AM, Audrey Hollinger wrote:


Amy,
Tablespoon-per-cup formulas can be scaled too! One tablespoon is 1/16
of
a cup, so a formula calling for, say 1 tbsp/cup is 6.25% (1/16 or 100%)
V/V.

Now I will point out that this is only an approximation, and one that
gets worse for higher percentages, since % V/V really means percentage
of solute within the finished solution, whereas the formulas are
usually
given as amount of solute as a percentage of the (pure) solvent. Few
recipes encountered in paper and book arts are of the form "mix powder
with [less than the full amount of water], then top up with more water
to [some specific volume]."

More concretely, the above formula likely produces more than a cup of
finished solution, so the actual V/V percentage would be less than
6.25%

To convert from V/V formulas to W/V, you need to know the bulk density
of the powder. Sometimes this is listed on a specifications sheet, and
sometimes on the MSDS. Lacking either, I have found that assuming a
bulk
density of 1 g/cm3 is close enough. The only powders in our shop that
are far from this are titanium dioxide and iron oxide based pigments.

Does either of these approximations matter? Probably not. Most recipes
have plenty of leeway in them, often ending with a recommendation to
add
extra water to suit. Differences in the water quality (e.g. mineral
content) can have dramatic effects on the viscosities of these
solutions, and individual recipes vary from one to another by more than
the error in these approximations. As well, other technical changes in
the usage of the solutions can adjust for varying solution strengths,
for example by adjusting the temperature at which the solution is used.

Unfortunately this general lack of technical rigour means that each
artist must collect their own set of custom-tweaked favourite recipes
by
trial and error.
-Kevin Martin
 the Papertrail

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*********************************************** The Bonefolder: an e-journal for the bookbinder and book artist

            For all your subscription questions, go to the
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                 Both at: <http://www.philobiblon.com>
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