Brian, There is certainly technical content in what you wrote, but to keep certain people happy, I have added the NTC. Most of us aren't even 59, let alone have any neat stories like that. Ever thought of writing an autobiography? Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis Sent: Saturday, September 01, 2007 3:31 AM To: [log in to unmask] Subject: [TN] OT: reminiscences When I was a student, in 1948, I took a summer job with a company making aircraft gyroscopic gunsights. My work involved: 1. mixing potassium bichromate with fish glue 2. applying a coat of this mix to a very thin blackened steel sheet 3. after drying, exposing same to UV light through glass photographic plates with registration pins, turning over and doing the same on t'other side (different plate) 4. developing the image with hot water 5. etching the sheet in nitric acid 6. rinsing in clean water 7. stripping the resist in boiling strong sodium hydroxide solution The result was about twenty graticules with two curved, very fine, slots. If two were placed back-to-back, depending on their respective positions, two dots of light shone through. These were projected on a half-silvered mirror and the gunner would turn a knob to align the two dots of light with the wingtips of the enemy aircraft, to get the range. This was a very hazardous job but it was my first (but not last!) experience of using a photoresist for etching a metal. Can anyone beat this kind of work, going back 59 years? :-) Brian --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------