[QUOTE=jochen;1443918]After my experience the 1:2/35 SMC Takumar is more difficult to clear than the 1:1,4/50. There remains a certain light warm tone. If the 35 mm gets too hot there is a strong risk for delamination of the rear lens element. The 50 mm seems to be more heat resistant.[/QUOTE

The Ikea Jansjo worklight http://www.ikea.com/us/en/catalog/products/20169658/ produces very little heat and works in removing the yellow caste on Thorium lenses like magic, and after you have removed it makes a very useful reading lamp all for less than $10.