As confirmed by Ryuji, PVA(H) wasn't discovered until 1924. This alone is sufficient to exclude it (PVA) from the constituents of Gloy which
appears in literature prior to 1920. One of the articles I read stated that Gloy was a mixture of Dextrin and Magnesium Chloride but doesn't
give any details. A more modern recipe is more precise being
Yellow dextrin (95% soluble) 65.7 pbw
Water 32.9
Tributyl phosphate 0.2
Heat to 88°C for 30 min, cool to 60°C, and add Corn syrup 1:1
It may seem that I'm being pedantic about this issue but I'm concerned that the product referred to in Alt Photo literature may not be the
product available now with the chance that the methods described in those tomes may not work as described. I also want (if I need to)
produce a colloid which works, using readily available every day products in my own kitchen :)
I did make some Dextrin a couple of days ago and in solution is very similar to Gum and Gloy. I have yet to test it photographically but all the
phyical attributes of Gum/Gloy are there.
Regards,
David H.
On Sun, 26 Mar 2006 09:51 , Katharine Thayer <kthayer@pacifier.com> sent:
>David, just out of curiosity, what do your sources say Gloy is made
>of, if not PVA?
>
>Products do change over time, as you say; my vague but perhaps
>imperfect understanding is that gloy was once made of gum arabic and
>later came to be made from PVA, just as Elmer's glue was once made
>from milk products (hence the cow logo) and later changed to PVA.
>
>The designation PVOH to distinguish polyvinyl alcohol from polyvinyl
>acetate may be useful here to help us keep them straight, but isn't
>a term used in the literature about dichromated polyvinyl alcohol,
>where it is simply referred to as PVA. There was a discussion here a
>year or two ago about the difference between the two; if you're
>interested you might look at that.
>Katharine
>
>On Mar 26, 2006, at 4:39 AM, davidhatton@totalise.co.uk wrote:
>
>> Hi Terry (and thanks to those who replied),
>>
>> It is from the horse's moth that Gloy is made up of PVA + a
>>
>>> plasticiser+a preservative.
>>>
>>>
>>
>> Personally I have a problem with horses finding them the least
>> reliable of creatures fit only to be rendered into glue as soon as
>> possible. The
>> reason for the headline is that I have reason to believe that this
>> is not the case No PVA in Gloy). I'm not a chemist but why does PVA
>> require a
>> preservative and a plasticiser? Is PVA not an adequate adhesive in
>> its own right?
>>
>> The my 'research' shows Gloy as a brand to be part of the
>> historical record at least as early as 1918 and I suspect that PVA
>> was not in the
>> mainstream of adhesive manufacture at that time. Could it be that
>> the current Gloy has been re-engineered in recent years with modern
>> components ? The original ingredients would have deteriorated
>> without a preservative I agree, but surely not PVA (unless the
>> plasticiser is
>> corn syrup or something).
>>
>> Any thoughts?
>>
>> David H
>>
>>
>>
>>
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>
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Received on Mon Mar 27 04:03:00 2006
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