Archive for April, 2014

Beating the Goo !

Monday, April 28th, 2014

Half inchSome while ago in 2010 I commented on the many problems facing people like me when trying to playback video archive material. The problem is that tape manufacturers never realised, in the mid 1970’s, that they had created formulations for magnetic tape that were going to cause problems in about 20 years time. Almost all of the video and some audio tapes held at Imperial are now suffering from what is called Sticky Shed Syndrome. It’s a great name for the Goo that comes off of the tapes when you try to play them. A report into this problem said “Somewhere between 20% and 80% of all U-Matic (video) tapes are showing obvious signs of decay or are giving the archives holding them cause for concern. U-Matic is widely considered by the major broadcast archives in Europe as the top priority format for video preservation. U-Matic transfers take between 1-2 hours of operator time per hour of programme material for tapes in good condition, rising to 5-10 hours per hour or more for difficult media.”

machineAll of this is what I’m now experiencing with batches of U-Matic videotapes that I’m trying to get onto DVD and then after that, onto the Imperial YouTube channel. What happens, when you play a tape, is that you will very rapidly start to hear the typical screeching noise of the tape sticking to interior parts of the recorder and you’ll soon be taking the cover off of the recorder, as seen on the right. At this point the tape will almost certainly have come to a complete halt all on its own. The ‘binder’, which holds both the magnetic oxide and the back-coating onto the plastic, is slowly breaking down. It’s absorbed moisture over a period of time and has gone slightly sticky. This is primarily because the tapes were never stored in air conditioned locations. Ampex is one of the companies that had the problem with sticky tapes (most of our tapes are from Ampex). In 1993, they created a patent for overcoming these playback problems by heat-treating tapes and I have now resorted to this approach. For those engineers reading this, here’s the extract from what they patented: “…Polymers can react with water from atmospheric moisture to break the ester linkages contained in such polymeric chains and form lower molecular weight polymers, a process known as hydrolysis. When a sufficient number of such bonds have been hydrolyzed and broken, the binder becomes undesirably weakened due to degeneration of molecular weight. The breakdown compounds of this weakened binder migrate, can exude from the coating thus causing the tape to be sticky and to shed.

bakingHeat treating or Baking as it’s called, is now considered (and used throughout the World) as a method for overcoming playback problems when most other things have been tried and failed. So, this week I attempted this approach myself. You need a way of continuously heating the tapes to between 50-54oC and for several hours. Not wanting a lab oven here at home (where I’m slowly transferring the archive) I resorted to the other suggested method of using a digital controlled food dehydrator. Ebay to the rescue and installation complete (pic above) my first attempt was carefully monitored with an external temperature probe cassetteduring the few hours that I heated the tapes for. I had partial success when running the first tape, but it needed a bit more treatment. I also discovered that the inside of the actual tape cassette has small plastic guides which were also getting goo on them. This was causing more problems than inside the actual tape machine. So, take the tapes apart (pic on right), clean the guides, heat them again, let them cool down and reassemble. Success with the first tape! It played back all the way through and was now onto DVD. The next tape was still causing problems and I soon discovered the typical screeching noise was now coming from inside the cassette rather than the playback machine. goo on guideLooking at the cassette I could see that the interior plastic guides were once again coated with goo (pic on left). I put my finger on the guide and it stuck there like sticky tape! So, after taking the cassette apart for the third time and cleaning the guides it played OK. Interestingly I’ve not found any references to these guides inside the cassettes being part of the problem, it’s only references to inside the tape machine. Anyway, the last tape is now onto DVD. A saga indeed and very time consuming (two days for two tapes), but a great feeling of success when I beat the Goo. Baking is THE way it seems. All I have to do is now work my way through the other few hundred video tapes. Incidentally, these current tapes are all from our Maths series made with the London Mathematical Society (LMS) and are now on the YouTube channel in the LMS Playlist. The picture below is of the first successful replay after heat treatment of tape number one. It needed a touch of tender care with TBC adjustments for brightness, colour, sharpness and so on, but looks pretty good after 27 years of being on a cupboard shelf.

playback 

Colin Grimshaw April 2014

Queen Mother opens Biochemistry 1965

Wednesday, April 16th, 2014

This is an update to the original entry earlier this year. Pathe have just released all of its archive onto YouTube, so I am now able to bring you the film clip direct and in higher quality, rather than going via their own website.

In November 1965 the late Queen Elizabeth the Queen Mother visited Imperial College to officially open the newly completed Department of Biochemistry, headed by Sir Ernst Chain (1906-1979).  What you will see are the original 1965 (silent) film rushes shot by Pathe News for its weekly newsreel, shown in cinemas at that time. These newsreels ended in 1970. It is to be assumed that the final edited film (if that ever happened) would have had a commentary on it, but this is all silent.

icimagesThis film record by Pathe is one of the few that were shot on campus at this time. Sequences include the arrival, at the old college Exhibition Road entrance; Sir Patrick Linstead (Rector), Sir Ernst Chain and Lord Sherfield (Chairman Governing Body) all greeting the Queen Mother upon her arrival. This film would have been shot some 8 months before the sudden death of Linstead. You will also see the very obvious building work taking place across the entire campus, with a complete gap where Sherfield and the library now stand. Finally and most importantly, there are shots of Chain in his laboratory, something that we do not have in our own archives.

Were you in the crowd that day? Maybe you are one of the students lining up to speak with the Queen Mother at the end of the film? If you are, then do let us know.

Colin Grimshaw April 2014

Dr Harold R Allen 1983

Tuesday, April 1st, 2014

Allen2Dr Harold R Allen came to Imperial College as a lecturer in October 1947 after completing a PhD at Cambridge’s Cavendish Laboratory. He made major contributions to the Physics Department but more importantly to the musical activities within the college.

In this interview, recorded in 1983 and not long before his retirement, he talks about the 1960 transfer from the old buildings occupied by Physics, to the brand new building on the corner of Prince Consort Road and Queens Gate. Physics was the first department within Imperial College to move into an entirely new building. As well as this, he discusses his colleagues that were in the department during his years as a member of staff. There’s an interesting anecdote too about the initial design of the Physics lecture theatre and columns that were originally planned, but which would have reduced vision across the entire space.

Physics BuildingSir Roderic Hill who was Rector the time (1948-1954), is discussed as being the person to have started what was then called General Studies. Lady Hill had discovered during a conversation with Dr Allen that he had an interest in music and asked him what was the strength of musical activities going on within the college. All of this lead to the formation of a choir to sing at the then newly created Commemoration Day, the purchase of a piano followed along with the creation of a ‘space for musical activities’. He became leader, organiser and treasurer of the college orchestra.

This interview was recorded in the Imperial College TV Studio on 18th July 1983, especially for the college archives. It was intended to capture the people and history of the college for others to enjoy in the future; we are doing that now, over 30 years later!

 

A piece of sad news from Linda Jones in the Blackett Lab is that Harold Allen died on September 5th of this year, 2014.

Colin Grimshaw April 2014