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Making indicator stop
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Frank Pittel
Mar 17, 2012, 7:52:14 PM3/17/12
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Earlier today I was at a local store and lost my head in the heat of the
moment! I ended up getting a gallon of glacial acetic acid and then went online
and ordered 10 grams of bromocresol purple dye to make an indicator stop.
Has anyone here made their own indicator stop and if so how much of the bromostresol purple
do I need to add to a gallon of 28% stock?
--
-------------------
Keep working dumbo needs the money
moment! I ended up getting a gallon of glacial acetic acid and then went online
and ordered 10 grams of bromocresol purple dye to make an indicator stop.
Has anyone here made their own indicator stop and if so how much of the bromostresol purple
do I need to add to a gallon of 28% stock?
--
-------------------
Keep working dumbo needs the money
Andreas Gugau
Mar 17, 2012, 7:58:04 PM3/17/12
to
Am 18.03.2012 00:52, schrieb Frank Pittel:
> Earlier today I was at a local store and lost my head in the heat of the
> moment! I ended up getting a gallon of glacial acetic acid and then went online
> and ordered 10 grams of bromocresol purple dye to make an indicator stop.
>
> Has anyone here made their own indicator stop and if so how much of the bromostresol purple
> do I need to add to a gallon of 28% stock?
Just a hint: Except you're doing a 100 papers a day, just use your stop
> Earlier today I was at a local store and lost my head in the heat of the
> moment! I ended up getting a gallon of glacial acetic acid and then went online
> and ordered 10 grams of bromocresol purple dye to make an indicator stop.
>
> Has anyone here made their own indicator stop and if so how much of the bromostresol purple
> do I need to add to a gallon of 28% stock?
one day and then throw it away. For developing film it's some 10 to 14
films and then change the stop. It really costs nothing.
Andreas
--
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Frank Pittel
Mar 17, 2012, 9:08:48 PM3/17/12
to
Andreas Gugau <ne...@andreas-gugau.de> wrote:
a printing session. I like the indicator in the stop since it reliably lets me know when the
stop needs to be replaced!
: Am 18.03.2012 00:52, schrieb Frank Pittel:
: > Earlier today I was at a local store and lost my head in the heat of the
: > moment! I ended up getting a gallon of glacial acetic acid and then went online
: > and ordered 10 grams of bromocresol purple dye to make an indicator stop.
: >
: > Has anyone here made their own indicator stop and if so how much of the bromostresol purple
: > do I need to add to a gallon of 28% stock?
: Just a hint: Except you're doing a 100 papers a day, just use your stop
: one day and then throw it away. For developing film it's some 10 to 14
: films and then change the stop. It really costs nothing.
: Andreas
When printing I dump the stop after each session but often need to replace the stop during
: > Earlier today I was at a local store and lost my head in the heat of the
: > moment! I ended up getting a gallon of glacial acetic acid and then went online
: > and ordered 10 grams of bromocresol purple dye to make an indicator stop.
: >
: > Has anyone here made their own indicator stop and if so how much of the bromostresol purple
: > do I need to add to a gallon of 28% stock?
: Just a hint: Except you're doing a 100 papers a day, just use your stop
: one day and then throw it away. For developing film it's some 10 to 14
: films and then change the stop. It really costs nothing.
: Andreas
a printing session. I like the indicator in the stop since it reliably lets me know when the
stop needs to be replaced!
darkroommike
Mar 16, 2013, 3:31:56 PM3/16/13
to
Indicator for Stop Baths
Bromcresol purple, 10% solution, 9.25 g
Sodium hydroxide, 1.0 g
Distilled water to make 250.0 ml
Add a sufficient amount of this solution to any amount of fresh 28% acetic acid to cause it to be clearly visible as yellow. When the pH of the acid becomes higher than 6.8 the bath will turn purple. Discard at the first signs of changing to purple or sooner.
An alternate method is to place 24.0 ml of stop bath to be tested in a container. Add 2 drops of the testing solution. If the stop bath remains yellow it is still good. If it turns purple time to deep six.
Caution: Dissolve the sodium hydroxide in a small volume of water in a separate container before adding it to the solution of the other constituents.
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