Re: tween 20

I know you are not the one who advocated Tween 20 as a coating aid, but
since you are not getting responses, I decided to comment on the choice
itself. Surfactant like this is not very effective as a coating aid (and
so I use different kinds of surfactants for this purpose). One problem
with many surfactants is that they spread on paper surface and reduce
the surface tension too slowly. Since we are running brush or glass rod
at a fairly fast speed, those surfactants are not very effective in
helping rapid, even spread of the sensitizer without leaving uncoated
spots. Another popular surfactant, Triton X-100 is also a poor coating
aid. (Tween 20 and Triton X-100 are excellent wetting agents, but not
very good coating aid.) One possible way to overcome this problem may be
to saturate the surface of the paper with the surfactant prior to
coating of the sensitizer, but why do we want to bother when we can pick
a better surfactant?

The one I use is a blend of two nonionic surfactants to reduce dynamic
surface tension while minimizing foaming problem. However, no company
sells this surfactant off the shelf at this time.

I also agree that Artistico Extra White is less absorbent, but I don't
find it any more difficult to coat than Magnani Pescia.

Ryuji

On Tue, 06 Dec 2005 20:44:21 -0700, "Christina Z. Anderson"
<zphoto@montana.net> said:
> Tween 20 is used to help traditional cyanotype absorb into the paper
> better.
> Some papers are not a problem. Fabriano Artistico is a bit less
> absorbent
> and the Tween helps the solution to sink in and not puddle on the
> surface.
> Chris
>
> Good afternoon,
> a quick question from a german cyanotype newbee. For what is Tween 20
> used
> in doing cyanotypes?
> Best regars from the cold and rainy Germany
> Hans
>
>
Received on Wed Dec 7 03:26:11 2005