Re: Mixing Ratio: 14 Baume Gum From Powder
It gets a bit more complicated than that, Michael. The old "2 in 5" was
variously interpreted as 2 in a combined 5 (e.g. 2 + 3) and 2 +5--very
confusing. One author wrote Demachy used "twice this density of gum" and
what he was saying (in checking Demachy himself, who also changed this ratio
in his practice) was that Demachy used 2 in 4, not 4 in 5. Argggghhhh.
So then I go back to the German literature, because they were the precise
ones verbally and in practice very much so. And when I found that the
Germans used all kinds of dilutions, 10%-50%, that's when I thought, heck,
pick what works for you and calibrate around it.
This is a very condensed explanation of about 8 pages on the topic I have to
date. More than anyone would ever want to read.
I find the commercial gums too thin so I mix my own, both 1+1 and 1+2, but
1+1 is definitely thick and glossy, and usually reserved for fattening up a
commercial gum if I use it in my practice (which I do because I have two
remaining bottles).
I haven't checked your measures below, but it is surprising the volume
difference between 288g and 320g gum! It is fairly lightweight. My guess is
you don't have to be quite so precise with the half grams and such, though.
:)
Chris
----- Original Message -----
From: "Michael Koch-Schulte" <mkochsch@shaw.ca>
To: <alt-photo-process-l@usask.ca>
Sent: Wednesday, August 29, 2007 10:04 AM
Subject: Re: Mixing Ratio: 14 Baume Gum From Powder
Just check my math here for me... So the old "2 parts gum to 5 parts
water"
(1:2.5) mixes a tad on the thick'ish side -- for me at least -- at this
point in my life ;^). The mixes you and Art cited are just a shade under
1:3
(to just a little above 1:2.6). Until my Baume-O-meter arrives I'm going
to
work with 7 g. in 20 ml. of water ~ 1:2.85. And maybe try 8.5 g. in 25 ml.
Sound about right?! Thx.
~m
RNP Arrays: Open Source Digital Negative Project
www.inkjetnegative.com
----- Original Message -----
From: "Christina Z. Anderson" <zphoto@montana.net>
To: <alt-photo-process-l@usask.ca>
Sent: Wednesday, August 29, 2007 8:03 AM
Subject: Re: Mixing Ratio: 14 Baume Gum From Powder
Hi Michael,
The answer to your question is to buy a $30 baume meter from Cole Parmer
and
also a test tube tall enough so it can be submerged mostly (about a
foot).
I've been communicating with Art Chakalis about this and he has a measure
of
288g gum to mix up a liter of combined solution. I found with my gum
arabic
approximately 840ml water to 288 made a liter. But Art pointed out that
different gums have different moisture content so that this measurement
is
never exact, hence the baume meter. But about 280-320g gum = 14 baume.
SO, I was on a wild goose chase about strengths of gum throughout history
and found that they varied from 10% to 50% gum! Take your pick.
Chris
----- Original Message -----
From: "Michael Koch-Schulte" <mkochsch@shaw.ca>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, August 28, 2007 11:01 PM
Subject: Mixing Ratio: 14 Baume Gum From Powder
> How do I mix ~14 baume gum from powder? It's not 1g. gum to 2 ml of
water
> that's about 18 baume so I've read....and I'm finding it too thick? A
> sub-question might be how could I water down a 1:2 mixture. So what do
> people do 1:3? 1:4? I read somewhere on the list someone (Guido) was
using
> 1:4.5
>
> ~m
>
> RNP Arrays: Open Source Digital Negative Project
> www.inkjetnegative.com
>
>