From: pete (temperaprint@blueyonder.co.uk)
Date: 02/21/03-08:49:23 PM Z
Jack,
The simple answer to your query is I just donšt know. I have tried
5% of acetic acid with little effect but this a weak acid in comparison to
sulphuric and I have not tried muriatic.
However I know that a 5% sol of hydroxide will also do the trick. Some
more scientific experimentation needs to be done. It may be that the strong
acid or alkali softens the tanned colloid allowing the oxidation by products
to leach out and desolve into the water solvent. all I am certain of is a
1% solution of sulphuric acid has neutralised the
yellowish/greenish/brownish stain in my TemperaPrint very effectively for
the past ten years with no apparent side effect.
Pete
> Pete:
> This is an interesting idea . . is it the acid? Could one use muriatic or
> acetic acids in place of the sulfuric?
> Jack
>
>> How about a 1% solution of sulphuric acid as a clearing bath this has worked
>> for me in my TemperaPrint process.
>>
>> Pete
>>
>>> Richard,
>>> One of the problems that I've always had with reversal deveopment is that
>>> I never seem to get completely rid of the yellowish/greenish/brownish stain
>>> left over from, I presume, the dichromate bleach, I've tried clearing baths
>>> other than just the sulfite with not too much success. I tried the
>>> permanganate bleach long enough ago that I've forgotten the results, but
>>> obviously they weren't encouraging. Naturally, there is always the odd time
>>> when everything comes out just right with no apparent change in technique. I
>>> think they (the great they) do that just to make us even crazier. Do you
>>> have
>>> any insight as to what might solve this problem?
>>> One of the reasons that I pursued reversal processing in the first place
>>> is that theory says that the more sensitive (and larger) film grains which
>>> develop first, are then removed in the bleach leaving the finer half of the
>>> silver bell curve to create the finished transparency. I would have to say
>>> that my observations tend to bear this out, and make it tantalizingly worth
>>> doing, especially with 35mm, and 4x5 can be extraordinary. They also bear
>>> out
>>> the fact that you have to be about as careful as is if you were exposing
>>> color transparency film if you want consistant results. Thoughts?
>>>
>>> Bob
>>
>
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