[alt-photo] Re: Gum...again!

[Katharine Thayer]

Hey Paul,
I've forgotten now what you said your exposures were for sunny  
southern California, but I do remember thinking at the time that they  
seemed awfully long to me, since even on the Pacific Northwest,   
which isn't known for intensity of sunlight, my sun exposures were  
usually less than a minute.

It's not that overexposure per se changes the color, it's that  
overexposure results in dichromate stain, which dulls the colors and  
needs to be cleared with a bisulfite compound.  But it's easier not  
to overexpose and not to have the dichromate stain in the first place.

Katharine


On May 14, 2010, at 4:33 PM, Paul Viapiano wrote:

> Hi all...
>
> I've been printing away here since my entry to gum one year ago,  
> exploring this and that and being accepting of the vagaries of the  
> gum experience, going with the flow, etc...and having a lot of fun  
> among the disappointments.
>
> But today, while experimenting with different papers for making  
> unwaxed paper negatives (I've been using waxed negs for gum for the  
> last few months or so) I ran across something which I don't think  
> I've seen mentioned; either that or I am totally losing my mind.  
> And that is how drastically overexposure can totally change a color  
> or certain colors.
>
> I'm used to seeing dull colors after development, nothing like the  
> brushed out color intensity of just pigment mixed with the gum, and  
> although I've tested exposure many times with my wedges, I don't  
> think it really hit me until today that not only will an  
> overexposed layer take longer to develop, it drastically changes  
> and dulls the original color.
>
> I think I've been overexposing all along...
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