Thanks for reminder, Paul. I add DABCO and azide. Give enough retardation of fading to allow a good session on the confocal to get plenty of images before bleaching sets in. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.726 / Virus Database: 481 - Release Date: 22/07/2004