Can you submit an image? I can imagine what this is but, no point until I see an image? What are you doing that is different, if this is a new problem? Curiously, Carl Carl Hobbs Histology Manager Wolfson CARD School of Biomedical Sciences Kings College London Guys Campus SE1 1UL Tel: 020 78486813 Fax: 020 78486816 020 78486813