Re: Microporous Inkjet papers, was Re: Yupo, was Re: Temperaprint & Gum

On 13 Mar 2004, at 14:29, Richard Sullivan wrote:

> Just for fun I coated it with some vandyke solution. I brushed it on
> and then wiped it off with a paper towel leaving only that which went
> into the holes. I suspect I printed it while part was wet so thus the
> streaks.
>
I looked at your image and found that it looked almost exactly like
a similar experiment I did trying to make a Van Dyke on *matte*
(ie, not "microporous") inkjet paper. Mine was completely dry, so I
don't think that your streaks were caused by moisture. I think they
are caused by loosening of powdery components from the ink
receiver layer.

In a microporous inkjet paper, there is a mechanical substrate
which is first coated with one or more ink receiver layers. These
layers usually contain kaolin along with other materials such as
gelatin, starch, pectin, cassein, etc., and various dye-fixing
cations, pigments, fillers, dispersers, hardeners, pH adjusters,
etc., etc.

The microporous layers are placed on top of the dye receiver
layers. When in ink drop strikes one of the holes it is conducted by
capillary action down to the receiver layer where it is quickly
absorbed and immobilized. The surface, therefore, becomes
effectively "dry" very quickly (much faster than the clay
undercoating). Moreover, since the ink is now fixed *below* the
surface, the image is rugged, and the paper can be manufactured
with glossy surfaces and still be practical.

I'm guessing that in the somewhat extreme case of coating one of
these papers, material from the dye receiving layer is lifted to the
surface and smeared around by the brush (or paper towel). Some
of the material remains on the surface and is free to react with the
chemicals in the coating solution. It will be interesting to see if you
notice any color shifts in parts of the image as time passes.

Regards,
Gary Nored
http://home.centurytel.net/Gary_Nored/
Received on Sun Mar 14 16:58:01 2004