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  #1  
Old 25th February 2011, 09:44 AM
hilly hilly is offline
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Default Gum Bichromate

Hello all you Gummists out there!
Just tried printing my first gum print using the Fotospeed kit. I managed to get one semi decent print using one colour but i am a little confused and hopefully someone can help me?
When trying to print more than one colour and i have my CMYK digital negs what negative do you use to achieve a particular colour? For instance do you need the cyan negative to achieve a blue colour?
I had been using the black for all colours as this had more density.
Also i could get a good exposure on the single colour leaving it expose for 7-8 minutes but when i tried to put another colour on top i was confused as to the exposure time, Can someone give me some guidance?
Thanks in advance.
Hilly
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Old 25th February 2011, 05:08 PM
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I am not familiar with the Fotospeed kit but I made (a long time ago) gum prints by mixing my own chemicals. The The colour of the image depends on the pigment colour mixed in with the gum arabic and bichomate and is not related to the negative colour. Subseqant exposures should be similar to the first exposure.
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Old 26th February 2011, 09:59 AM
hilly hilly is offline
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Thanks Barry, my method was to mix gum,bichromate and colour leave to dry and then expose for 7 mins. I would then mix gum,bichromate and a different colour, leave to dry and expose i did expose again for roughly 7 mins then wash but only the first colour could be seen.
Oh well, back to the drawing board!!
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Old 27th February 2011, 11:28 AM
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Sounds like you are doing the right thing Hilly. There is more information here that may be of help?
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Old 10th March 2011, 08:19 PM
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http://pacifier.com/~kthayer/html/tricolor.html
or more specifically
http://pacifier.com/~kthayer/html/RGBseps.html
"Cyan = minus Red; Yellow = Minus Blue, etc." But this is for separation colours, if you just want to print one colour, just print a negative in 1 colour?
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Old 17th March 2011, 11:48 AM
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Click image for larger version

Name:	gumcoke.jpg
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Size:	71.4 KB
ID:	1082

This is my attempt at gum with two colours. The first dev was with red pigment pea sized then exposed for 8mins.The next step was to use yellow separation digital negative and yellow pigment half pea size and only exposed for 4 mins.
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Old 17th March 2011, 11:52 AM
hilly hilly is offline
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Quote:
Originally Posted by Akki14 View Post
http://pacifier.com/~kthayer/html/tricolor.html
or more specifically
http://pacifier.com/~kthayer/html/RGBseps.html
"Cyan = minus Red; Yellow = Minus Blue, etc." But this is for separation colours, if you just want to print one colour, just print a negative in 1 colour?
Thanks for the links will take time to read all the info carefully as at the moment i am just jumping in there and flailing wildly !!
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Old 28th February 2013, 02:33 AM
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kevsNorthants kevsNorthants is offline
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Those urls are dead now - the site is (as of Feb 2013) here:

http://katharinethayer.com/
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