Re: Snow in South Carolina, was Re: precipitation of dichromates

Sandy,
     Are you going to bring your 20x24 camera outside to photograph this???
     Alas, Ansel will have to wait. I have to sit inside at my computer
printing out tricolor separation negs for gum printing. Midterm reviews are
on tuesday...
Chris

----- Original Message -----
From: "Sandy King" <sanking@clemson.edu>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, February 26, 2004 8:11 AM
Subject: Snow in South Carolina, was Re: precipitation of dichromates

> Chris,
>
> When it snows in South Carolina, even an inch or so, school is
> cancelled, regardless of what the administrations says or does!! It
> is called self-cancel, carried out by the students with a compliant
> faculty. Seriously, no way I am going to leave the comfort and safety
> of up home and venture out on the roads around here when there is
> snow. That would be like playing demolition derby.
>
> But the great thing about snow here is that it goes away quickly. The
> forecast is calling for up to eight inches or more of snow here today
> and tonight, but up to the high 60s by the weekend.
>
> Now forgot about your classes and pretend that you are Ansel in Yosemite.
>
> Sandy
>
>
>
>
>
> >Thanks, Marek.
> >
> >Why would pot di be insoluble in alcohol and am di not? If this is too
> >complex an answer, don't bother...I'm just interested.
> >
> >In the old BJPs it was talking about the two at a time when pot di was
the
> >norm, and how pot di, because it is so low in saturation compared to am
di
> >(10 vs 30%), with a drop in room temp you tend to get crystallization
around
> >the bottle stopper all the time. That's always plagued me, too, in a
> >inconsequential but messy way with using saturated solutions, so I
thought
> >that'd be another goood reason to use am di at lower than saturation
point.
> >And then I came across this alcohol statement and was wondering.
> >
> >Can't believe it--it is SNOWING here in SC. Looks like MT outside....I'm
> >waiting to see if school is cancelled. In MT it'd have to be 2 feet of
snow
> >and 30 below zero before they'd consider closing anything.
> >Chris
> >----- Original Message -----
> >From: <mmatusz@pdq.net>
> >To: <alt-photo-process-l@sask.usask.ca>
> >Sent: Tuesday, February 24, 2004 1:36 PM
> >Subject: Re: precipitation of dichromates
> >
> >
> >> Chris,
> >> Potassium dichromate is insoluble in alcohol, ammonium dichromate is
> >> soluble, although I do not have the exact solubility numbers. You gum
> >> solution is mostly water anyway. If you like to print with
concentrated
> >> dicromate solutions (around 15% in the final solution or even
higher)then
> >> it is likely that you can not add a lot of alcohol, or else potassium
> >> dichromate will precipiate. Again the alcohol addition is also small,
> >> maybe 5%. If you are printing with a dilute dichromte solution you
might
> >> not have a problem with potasssium dichromate and alcohol. This is one
of
> >> those things that it is so much easier to test in practice anyway.
> >> Happy printing
> >> Marek Matusz, Houston
> >>
> >> > Do any of you chemists out there know why potassium dichromate would
> >> > precipitate out of solution when alcohol is added vs. ammonium
> >dichromate
> >> > which doesn't? Could it just be potassium's lower saturation
point
> >that
> >> > makes it seem that way or is there a property of alcohol that makes
a
> >> > potassium form do this whereas an ammonium form doesn't? Or is this
even
> >> > true in your observations, and from a practical standpoint, at what
> >point?
> >> > Any conjecture would be appreciated.
> >> >
> >> > My reason for asking this is just thinking about the addition of
alcohol
> >> > in
> >> > a coating solution in gum printing that has been suggested in the
past,
> >to
> >> > make it thinner and easier to coat, whether this is viable with
> >potassium
> >> > dichromate.
> >> > Chris
> >> >
> >> >
> >> >
> >>
>
Received on Thu Feb 26 07:29:58 2004