The best thing I've found about keeping ALL your work squirreled away in boxes (the good, the bad and the downright ugly!) is that when you want to try a new technique, or maybe one you've dabbled with before but not quite got it right, you already have a decent stock of pieces that you can play with without fear of disaster. This was the case recently when I decided to have another go at toning some of my cyanotypes. Toning is a good option when you have under exposed or over exposed results from your dried cyanotypes. If the print is too light you can simply soak it for a bit & stick it in a toner bath for a bit to darken it down and change the colour from the traditional cyanotype blue to brown/red/black/green depending on what toner formula you are using. Coffee, black tea or green tea are the easiest as most people have them around the house already. I had three underexposed prints like this so I soaked the prints for a bit in clean water then stuck them in a coffee bath for between 1 and 2 hours.
Also in my box of rejects I had several 2-3 year old cyanotypes that were way too dark so I bleached those back for a few minutes using a bath of soda crystals and water until they were a fair bit lighter and then toned them in the same coffee based solution I'd used the day before. The other experiment involved embossing a shape around the prints while the paper was still a bit damp to give a kind of printing plate look. Needless to say I have never tried this before so it didn't go quite as well as planned (plus I did in on the front of the print and not the back which looked terrible) so that particular experiment looks like it needs a bit more refining. Every day is a school day.