Re: Stock Paint:Gum Solutions?
Hi Alberto,
Good point.
My parts are weight parts indeed.
kees
On 24 okt 2008, at 08:41, Alberto Novo wrote:
This discussion about baume, concentration etc. periodically returns
on the list. I myself have had some difficulties the first time I
started printing gum, because very often the concentration is
expressed in a fake percentage, like 30% for a mix made from 30 g of
gum plus 100 mL of water. For me, as a chemist, this was very
puzzling because this is not 30% but 30/(30+100)= 23% weight/weight.
Also very confusing is parts/parts, because the units of such parts
are not declared. Is it weight/weight, or volume/volume? In the
first case, 1+3 leads to 25% w/w, and 1+2 leads to 33% w/w.
Dirk-Jan: your 30% gum, which is for me a 23% w/w, is very close to
Kees' 1+3 (if both parts are weights, it is my 25%) and the
respective Baume degrees are quite consistent.
Alberto
Hi Kees (and others), When you're tired of converting the
hydrometer results to baumé:
in the better cooking shops, you can find baumé meters that are
used for
measuring the syruppy of sugar-melts/caramel kind of mix..
I bought mine for about 7 euro's :-)
My 30% gum solution (30 grams gumbrick dissolved into 100 ml
distilled
water) turned out to be 13 baumé Dirk-Jan 2008/10/23 Kees
Brandenburg <ctb@zeelandnet.nl>
Hi Marek,
That's a bit confusing. When I measured my former mix (1 part gum
+ 3 parts
water) some year ago when Chris asked us about our gum mixes it
turned out
to be near 14 baumé. Now I use a heavier 1 part gum + 2 parts
water mix.
As I have both concentrations at hand I just (re)measured both
mixes with
my simple winemakers hydrometer.
these are the results:
My 1+3 mix has a specific gravity of 1.101 this is 13,3 baumé
My 1+2 mix has a specific gravity of 1.132 this is 16,9 baumé
You can lookup the baumé grades here:
http://ilpi.com/msds/ref/baumescale.html
And some pictures from the lab:
http://polychrome.nl/techlog/gum-concentration
kees
On 23 okt 2008, at 16:40, Marek Matusz wrote:
Kees,
I use 14 baume ready gum solutions (about 30% as I recall), so it
is the
same as yours 1:2.
Marek
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