I have been frustrated with my recent efforts when thiocarbamide toning ilford multigrade warmtone fb. I am aware of the dangers of too strong a bleach attacking the highlights so have made up a solution of 1:49 to avert this. After immersing the prints in the bleach for only 30 seconds I am still losing my highlights (from about zone 7 up on the grayscale). What am I doing wrong. Is my bleach too strong, or should I reduce the time in the bleach still further? Any help gratefully received.
The bleach needs to be weaker. Throw some old rejected prints into the bleach to take the edge off and slow down the process or continue to tweak the dilution ratios until it reaches the control point you desire.
As you suggest you can also reduce the time in the bleach. Toning is really like "playing in a sand box". Especially when it comes to color shifts and warmtone papers.