Digital BW, The Print

t_j_l_s wrote:
> Most aluminum compounds are rather chemically active.  Does anyone have an opinion on 
> what to expect in terms of print permanence from papers like the reportedly wonderful 
> looking new Harman that uses an "Alumina" coating to control ink absorbtion?
> 
> Thor

There's no independent fade testing of any of the Baryta 
(barite) papers including the ones with Alumina top layer so 
it will be difficult to get that information.

Henry Wilhelm says something about Barium Sulfate versus 
Titanium DiOxide and analogue RC papers but it goes a bit 
further than just RC papers. Interesting comments about 
Barium Sulfate and the use of OBAs in the second one.

http://www.wilhelm-research.com/phototechniques/PhotoTechniques_WIR_2005_01.pdf

http://www.wilhelm-research.com/pdf/HW_Book_17_of_20_HiRes_v1a.pdf


on Alumina: you can get a paper with two articles on Alumina

http://www.imaging.org/store/epub.cfm?abstrid=34162

http://www.imaging.org/store/physpub.cfm?seriesid=5&pubid=670

Degussa AG most likely is the supplier of what we see used 
right now, they have more varities

http://www.patentstorm.us/patents/6808769-description.html

You could make your own coating and tests based on that 
article :-)

The Alumina (or actually the manufacturing process) is in 
the first place created to give a gloss surface by its 
uniform, small particle size. I'm sure they will have tested 
the other aspects like fade properties as well. The PVA 
mentioned as the binder for the Alumina has good properties 
and is used in inkjet inks as well.

Aluminium pure is chemically active as it easily oxidises in 
a variety of environments. But quite inert in its oxidised 
form. What could be interesting to the use with inkjet inks 
is the anodising-eloxal process to give aluminium a nicer 
more durable finish with or without color. In that case 
several dye types are also used, see dyes at the bottom of 
this webpage article.

http://en.wikipedia.org/wiki/Anodising

The layer is afterwards sealed by further expansion of the 
top surface, encapsulating the dye component.



-- 
Met vriendelijke groeten,  Ernst


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