Don't know the filter values but I would suggest that you cut some plain glass to size and then cover with rubylith which is red masking material used for filtering with lith films and line art processes. In the UK I bought some called AdMask which is sticky on one side. That should do it and its a cheap option. The rubylith will come in handy for other masking in the darkroom from time to time. ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.