Re: Fog test. Was: Re: Making Digital Negatives (safelights for Pt)

Tom Ferguson (tomf2468@pipeline.com)
Wed, 29 Jan 1997 18:25:08 -0800

Jeff, Eric, and others: thanks for the responses. I do use a five minute
still water rinse in between my developer and my first clearing bath
(sorry, I left that fact out of my post). I will try the "H3PO4
(phosphoric acid, reagent grade)" first, and then the distilled water if
needed. The EDTA comes from Bostick and Sullivan, and is I beleive "Tetra"
type. My clearing baths go "gray" as they are used, I don't believe they
get cloudy. But I will test as suggested ("Add a small amount of rinse
from your coating devise , brush or rod, to some of your "tap" water"), and
will report back. Thanks, dispite some recent grumbling, this list is a
great place and a wonderful resource.

tomf2468@pipeline.com

>Tom Ferguson wrote:
>...
>> Standard Bostick and Sullivan chemicals, grade 5, half platinum, half
>> palladium, on Cranes Platinotype paper.
>...
>Clearing was three 5 minute
>baths in EDTA (3 teaspoons per liter of water).
>...
>> The problem with testing, is it always seems to show you something you
>> didn't expect. Someone in this thread (Jeff ?) said that developing the
>> paper with tape on it (to avoid getting chemicals on a section of the
>> paper) was not only a way to test for safelight fogging, but if you
>> developed a piece that hadn't been exposed to any light, it was a way to
>> test if your clearing was complete. Unexposed paper in my situation does
>> show a very slight "stain", compared to the "virgin" paper under the tape.
>> I tried doubling my clearing time (three 10 minute baths), without any
>> change.
>
> Jeff wrote:
>Tom,
>May I suggest you try the following to clear prints on Craines
>platinotype paper.
>
>A) place print in tap water for at least 5 minutes. (maybe 10)
>B) place print through three 10 minute baths of H3PO4 (phosphoric acid,
>reagent grade from chemical supplier), mixed 2 ounces acid in 1 gallon
>water. I find that H3PO4 works best for clearing.
>C) wash
<SNIP>
>
>Note: If you omit the tap water bath, I find that the B&S Crains
>business card stock (special run) (what you call platinotype) takes an
>hour to clear. For some magical, yet unknown reason the tap water bath
>cuts the clearing time in about half. Try the test again and let me
>know. I get no decernable stain when clearing this way.
>
<SNIP>
>Jeff

On Wed, 29 Jan 1997, Eric wrote:

<SNIP>
Tom and Jeff
If your prints are hard to clear, I would recommend that in place of tap
water, you use distilled or purified water for at least the first clearing
bath. This should help eliminate the solids that are building up in the
paper reacting with the iron. (Does your clearing bath get cloudy? or just
brown/yellow in color?)

Try this test.
Add a small amount of rinse from your coating devise , brush or rod, to
some of your "tap" water. If it clouds ups, you should consider using
distilled water for at least your first, and perhaps second clearing
baths. You should notice that your prints clear much easier.

<SNIP>
>
What type of EDTA are you trying to clear with. Tetra? Di?

<SNIP>