Yes, they do, that is one of the reasons why fixing is so fast when they are used. But it would be more appropriate to say that they cause more swell rather than more softening if used properly. If used improperly both can take place.Originally Posted by Gerald Koch
However, in spite of this they can be very effective up to 100 deg F (~40 deg C), and they don't harm color film emulsions.
After all, that is the C41 process temperature.
You will have to be careful with B&W emulsions.