[alt-photo] Re: More on gum print

[Don Bryant]

>
I size with Knox unflavored gelatin and chrome alum.
>

I would definitely ditch the chrome alum. It takes days to completely harden
the gelatin (maybe why you had flaking) and produces a slight lavender stain
on the paper - not pretty.

>
I use a 1.5 ltr Crock Pot to keep my sizing hot (it has other uses in the
studio as well, just don't use it for cooking!)  Once the gelatin has
completely swelled and I'm sure I won't have any granules left over, I turn
the crockpot on high and let it do its thing.  When the gelatin is ready, I
still in the chrome alum solution.  Some sources suggest you should let the
gelatin/alum solution stand for a couple a few days afterwards but to be
honest, i haven't notice a difference one way or another.
>

If your flaking problem continues or is intermittent increase the gelatin to
5%. Knox gelatin will work fine but higher bloom gelatins can be used if
needed or available. It's actually cheaper to purchase 250 bloom gelatin in
bulk than Knox gelatin purchased at the food store.
 
Add 10 ml of grain alcohol per liter of gelatin to help dissolve the gelatin
and reduce or eliminate sparkles.

> 
I use Fabriano Artistico paper, which I pre-shrink by soaking in hot water
for 30 minutes).
>

Don't use hot water, just use tepid (70F) water for 30 minutes. Dry and do
it again
I work with parent size sheets so it's much less work in the end to
pre-shrink. Some people don't preshrink this paper, as Diana pointed out.

I use 37 ml of the gelatin size per parent sized sheet. I coat with a a wide
foam brush, 3 or 4 inches, side to side and then top to bottom to ensure an
even coating
I give each sheet one coating of gelatin, let it dry completely, then a
second coat. The gelatin is heated to 140F and held there during the coating
session. At the end of the session any remaining gelatin size is thrown
away.  Oh yeah, anytime you use glut best practice is to use full eye
covering, better yet use a face shield in a well ventilated area. I coat in
my open garage during warm weather and use a fan to create a positive
airflow, constantly moving air past the work area so fumes do not linger

>
Of all the sizing methods I've tried, including variations on acrylic
medium, etc. this seems to work the best for me.  Plus with reasonable
caution, until glyoxal or formalin, you don't need industrial ventilation..
>

Over the years chrome alum sizing has been shown to be less than reliable.
By example, your results probably demonstrate that. Chrome alum isn't
necessarily non-toxic.

Various types of PVA can be used as Loris points out. If you don't want to
use glut then use a water based PVA size. I'm not sure it's as durable as
glut but it will work very well.

Search YouTube for a demo video made by our own Jeremy Moore showing how to
size with Gamblin. 

Gamblin seems to work on most papers that can be coated easily.

Hope this helps,

Don Bryant