Re: gloy for tricolor on yupo?

Nearly all of this can be found after a five minutes on Google.

What is perhaps significant is that, contrary to wjat has been suggested
here, those with everyday experience quite happily refer to PVA as a gum, and
specific gravity is a factor in the expression of viscocity even in industrial
measuring devices,

We also learn that gum arabic has a heavier molecular weight than PVA, and
that one can buy PVAs with a wider range of molecular weights than has been
suggested here and so on.

So what is the purpose of the correspondence here ? In what way does it
further our objective of making gum prints ?

Terry

In a message dated 3/4/06 7:27:53 pm, kthayer@pacifier.com writes:

> On Apr 2, 2006, at 5:10 PM, Ryuji Suzuki wrote:
>
> > From: Katharine Thayer <kthayer@pacifier.com>
> > Subject: Re: gloy for tricolor on yupo?
> > Date: Sun, 02 Apr 2006 09:01:18 -0700
> >
> >
> >> [...] gloy is PVA, a very simple and well-understood polymer, mixed
> >> with some other stuff,
> >>
> >
> > Since you called gum arabic "extremely complex" and "not entirely
> > understood and somewhat indefinite structure," I would add that PVA is
> > also complex and somewhat indefinite structure.
>
> Point taken;  I was speaking relatively, not absolutely. While PVA 
> may be complex and somewhat indefinite, it is remarkably simple and 
> definite relative to gum arabic, which for starters has three 
> components each comprised of different material and each with a 
> different approximate molecular weight and a different structure.  
> The below description of the structure of gum arabic is taken from my 
> website page on the chemistry ot gum printing, which is still waiting 
> to be uploaded because I still keep hoping to discover something 
> definite I can say about it:
>
> "The first component, which comprises around 90% of the gum, has a 
> molecular weight of around 250,000 and contains virtually no amino 
> acid; its structure is globular and highly branched. The second, 
> comprising around 10%, has a molecular weight of 1,500,000 or so, 
> contains about 10% protein, and is thought to have a structure of 
> five globular lobes of carbohydrate, about 250,000 mw each, which are 
> attached to a common polypeptide chain.  The predominant amino acids 
> in this portion are hydroxyproline and serine. The third, comprising 
> less than 1% of the gum, contains 20-50% protein but is not degraded 
> by proteolytic enzymes, suggesting that the protein is located deep 
> within the "molecule", available neither to be attacked by enzymes 
> nor to participate in crosslinking.  The molecular weight of this 
> component is about 200, 000, and is highly compact. The predominant 
> amino acids in this fraction are aspartine, serine, leucine, and 
> glycine."
>
> The above description is my summary from several sources, including 
> the following.  I commend those interested to read the original 
> sources instead of arguing with me about whether the above 
> description seems "right" to you.
>
> (1) P.A. Williams, O.H.M. Idris, and G.O. Phillips. "Structural 
> analysis of Gum from Acacia Senegal (Gum Arabic)". In Cell and 
> Developmental Biology of Arabinogalactan-Proteins. Edited by Eugene 
> A. Nothnagel, Antony Bacic, and Adrienne E. Clarke. NY: Kluwer 
> Academics, 2000.
>
> P.A. Williams amd G.O Phillips. "Gum Arabic." In Handbook of 
> Hydrocolloids, edited by G.O. Phillips and P.A. Williams. Cambridge 
> (UK): Woodhead Publishing, 2000.
>
> (11) A. Bacic, G. Currie, P. Gilson, S.I. Mau, etc. "Structural 
> Classes of Arabinogalactin-Proteins" In. Cell and Developmental 
> Biology of Arabinogalactan-Proteins." Edited by Eugene A. Nothnagel, 
> Antony Bacie and Adrienne Clarke. NY: Kluwer Academic, 2000.
>
>
> >
> >> while gum arabic is an extremely complex arabinogalactan protein,
> >> with an enormous, not entirely understood and somewhat indefinite
> >> structure.
> >>
> >
> > Gum arabic is not a protein.
>
> Now there's a categorical  statement. I would tend to agree  that it 
> seems odd to classify gum arabic as a protein; I would be more likely 
> to classify it as a complex polysaccharide, since 98-99% of it is 
> comprised of monosaccharides, (the bulk of these galactose, 
> arabinose, rhamnose, and glucuronic acid) and only 1-2% is amino 
> acids.   But you and I don't get to decide how to classify it, and it 
> is in fact classified as an arabinogalactan protein. See:
>
>   P.A. Williams, O.H.M. Idris, and G.O. Phillips. "Structural 
> analysis of Gum from Acacia Senegal (Gum Arabic)". In Cell and 
> Developmental Biology of Arabinogalactan-Proteins. Edited by Eugene 
> A. Nothnagel, Antony Bacic, and Adrienne E. Clarke. NY: Kluwer 
> Academics, 2000.
>
> > Gloy and gum arabic may behave the same, and the crosslinking
> > mechanism may well be the same (although this is only a hypothesis)
> >
>
> When the crosslinking of PVA is now reported to vary if moisture is
> present, how can you make such a statement?
>
> Sorry, I'm having trouble keeping up; I'm not sure I'm seeing all 
> your posts.   Okay, so new information about PVA crosslinking makes 
> it unlikely that PVA crosslinking and gum arabic crosslinking are 
> similar, so you would no longer cite literature on PVA crosslinking 
> to answer questions about gum crosslinking? In which case, we don't 
> even have a clue about how crosslinking occurs in gum.
>
> (Note to Terry: when I refer to gum, I always mean the specific  
> substance known as gum arabic, or gum senegal, unless I refer 
> specifically to another gum like xantham or tragacanth).  To me it is 
> not useful to construct a vague class of substances that "work" in a 
> dichromated colloid process and call everything in this class "gum"   
> whether it is  gum or not; the only possible result would be 
> confusion.  If it floats your boat to say that you are engaged in gum 
> printing when you're using something other than gum, I have no 
> problem with that; you can call the process anything you like. Call 
> it a gum print, call it a Terry-print.  But to call it a gum print 
> and then extend that argument to say that because it is a gum print, 
> then therefore PVA is gum,  is illogical. PVA is PVA; gum is gum.)
>
> Katharine
>
Received on Mon Apr 3 14:01:23 2006