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Are you trying to print a tri color or one color image?
What do you men by "does not develop up in strength"? is it each print layer (Blue, Yellow, Magenta for tri color) or the final overall print result after all 3 layers printed or are you talking about your negative density?
What is your pigment ratio to gum? In one workshop I took they liked to use a very pale palette. I wanted stronger color results so I have now changed to more pigment in my pigment to gum ratio.
I am sure you know every gum person uses very different methods in achieving their desired print results.
if you could post some of your print results that would help to understand your problem.
Also- I recommend you get Christina Anderson's book "Gum Printing and Other Amazing Contact Printing Processes". Its a good resource and explains her technique for making gum prints.
Other Gum printers on this web site, that are far more experienced that me, can add their thoughts to your issues.
Good luck!