This is an interesting article reblogged with the kind permission of my friend Andrew Sanderson. There are a few different ways of intensifying a thin negative to improve it but Andrew has chosen to speak about thiocarbamide toning in this case.
Andrew is an Ilford Master Printer so really knows his stuff. He writes about photography and techniques at his blog, The Web Darkroom, so please feel encouraged to pay it a visit and leave a comment if you do.
By Andrew Sanderson
We try our best as film photographers to get a correct exposure every time but occasionally there are times when we inadvertently cock it up. It may be because we have forgotten to add extra exposure for bellows extension or a filter factor or the fact that long exposures need a calculation for reciprocity failure.
Sometimes light meters may be set to the wrong ISO/ASA. Then of course there might be a problem in processing with temperature drop, out of date chemicals or just bad luck. Whatever the reason, we have a thin neg and it is a problem to get the tones that we require in the print.