Digital BW, The Print

pr_roark schreef:
> "Mark" <mark@...> wrote:
> 
>> RC Papers commonly use Titanium dioxide as the whitening agent ...  When low levels of light strike the TiO2, free radicals are released that eventually embrittle the resin coating...
> 
> 
> I've experimmented a bit with TiO2 on the Arches to accomplish localized and controlled brightening (to subtly pull the eye into the print).
> 
> Do you think the TiO2 would pose a risk to either the Arches or carbon pigment?
> 
> 
> Paul
> www.PaulRoark.com 
> 
> 

I'm sure Mark has a more thorough reply,

I think the answer to that is more complex. Before barite was introduced 
in inkjet papers TiO2 was used and still is used as a whitener in all 
kinds of inkjet papers. So the addition of TiO2 may not be that 
problematic. It is in its use in the polyethylene barriers of RC papers 
where the problem lies. Polyethylene has many nice qualities but it can 
oxydise, it isn't very UV stable and it doesn't create an easy bond with 
other materials. Since the seventies there has been a lot done to 
improve the RC papers. Other TiO2 versions (anatase-rutile), blendings 
of TiO2 and other whiteners, copolymeres instead of pure polyethylene.

BTW,  RC papers show better results than non-RC papers if ozone fading 
of colorants is measured. Dye and pigments.  Colorants including OBA 
dyes, and the influence depending where the OBA is located in the sandwich.

It has been discussed before on other lists and there has been a thread 
on the subject here when the first barite papers were introduced.
Question then was whether barite would be a better component in inkjet 
papers than TiO2. I thought it wasn't and I do not think that has changed.

-- 
Met vriendelijke groeten,   Ernst


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