Quote Originally Posted by Neil Miller View Post
That's a hard one, Mike!

It seems that shrinkage is proportional to the amount of alkali present in the mix, which also introduces the other forms of Cellulose, namely the early (and dangerously explosive) cellulose nitrate which releases nitric gas during breakdown, to its safer alternatives of Cellulose biacetate, cellulose acetate and cellulose triacetate which release acetic acid and give a vinegar smell during breakdown, to a hybrid cellulose actetate nitrate. All of these would have had varying degrees of alkali within them and therefore different shrinkage rates. Shrinkage (and swelling) occur during a transitional phase, and even heat and micro-environmental differences will affect it.

Because a lot of these cellulosic plastics were used in the motion picture industry and the explosive nitrate mixtures and the corrosive acetic acid (vinegar syndrome) acetates had to be overcome, the Eastman-Kodak company ploughed a lot of research, money and man-hours into this. They came up with a water retention rate of 2 to 3 per cent for freshly made cellulosic plastics, which had to be reduced to 0.03% or under for maximum efficiency.

Part of E-As research involved chopping up preformed cellulose films or sheets (they sheet extruded cellulose up to 6inches thick) and putting this through a small bore injector with a heated barrel, heating up the pellets and effectively melting them together before they went into a screw-operated processor. Drying times in dry air (all moisture removed) and slight heating (high heat was never used in case the material deformed) was given as anything between 2 and 8 hours. However, they were making a base for film stock, which is transparent and very thin, so these drying times and possibly the processing methods themselves are not applicable to razor scales.

Which is one of the things that irritate me. people must have been trained in this and it was still in use in the 1950s and later, so we ought to know how it was done - but we do not. We know the general principles of its formation and use, but these are too broad for something as specific as razor scales. With that in mind, there were plenty of thermo-setting plastics, including the original plastic - horn, so there must have been 10s of thousands of dies, presses and moulds - where are they all now? A handful have turned up, notably in France and Solingen, but the American and British cutlery industry was enormous so one would expect at least a few presses, dies, etc to have survived, along with training manuals and old-timers first-hand experiences of using them. The devil is in the detail, and in this case both the devil and the detail are well hidden.

Regards,
Neil
Neil, there is so much good information in this post! Some excellent research on your part and some baffling points to ponder! The potential generation of explosive nitrates as side products in the early manufacture of these plastics has always impressed me. Since the origin of celluloid predates the origin of trinitrotoluene, I'd bet there were some catastrophic manufacturing accidents (to wit, explosions) in the early development and manufacture of early plastics that were at the time, quite mysterious and unexplainable.

I find Eastman Kodaks work to reduce the water retention in their celluloid to be a great bit of specific information. Water, as polar as it is, is not something we want mingling with our nitrates if we expect our material to not simply dissolve. The fact that they had to allow their film stock to air dry for 2-8 hours tells us a bit about the times our much thicker razor scales would have taken to become stable enough to handle. We could probably estimate 10-20 times that based on diameter alone in very broad and general terms.

I worry. About a lot of things that probably don't matter to most folks. One of my biggest worries is that every minute, or second for that matter, somebody passes with knowledge that they alone may possess. Lost knowledge is a tragedy of huge magnitude in my opinion. One of my nerdier past-times is operating a huge cross-compound Corliss steam powered pumping engine at a nearby annual event (they can only afford to bring steam up for a week a year ). I've often said, a person could teach a course in thermodynamics and mans quest for perfect Carnot efficiency using that engine alone. This thing was built in the '20's, and attains about 45% Carnot efficiency! Internal combustion engines attain about 15%, and yet, in 1920, these guys were producing the best efficiency numbers for a practical heat engine in human history. The knowledge the designers had about the gas laws as they were still being defined is absolutely mind blowing. Their math was perfect. Their craftsmanship, unreproducible today. We simply don't have the capability to forge castings the size that would be required. And these castings are all finished, the moving bits machined and polished to mirror surfaces, and the sheer number of unnecessary yet beautiful brass accents is astounding and unthinkable today. If you've ever seen Corliss valve gear in motion, you wonder if they had to bring in Swiss watchmakers to time the thing. Those guys were smart, incredibly hard working, and took great pride in the fruits of their efforts. And they're dying every day, taking their knowledge with them.

As to the evidence of their labors, I suspect war time metal drives had lots to do with this. And scrapping in general.


Quote Originally Posted by Neil Miller View Post
Came near to it on a couple of occasions. I ran out of 100% certified cotton wool when nitrating cotton to make collodion once and hastily resorted to what were described as 'photographers pure cotton gloves for handling film'. Judging by the billows of thick orange smoke that boiled up into the air, corroding everything it touched, the purity of the gloves was a little questionable.

I used to carry out experiments like this over a photographers sink - about 2 ft 6" wide by 6ft long by 1ft deep - it was filled with water and all I had to do was pull the home made lever that held the tray that held the flasks above the water and the smoke stopped. Luckily my respirator was up to the task - I could hold my breath for a very long time, else bye-bye lung linings.

The dark room was in a room off the bedroom - I had converted it into a lab. My wife went mental when she saw the damage. Well, to be honest she smelled it first, its smell hung in the air for days. It had stripped off the wallpaper and bubbled up the paint. Protestations of a makeover were not even entertained, and that particular avenue of enjoyment was cut off to me, for ever I thought. Until I built the shed, that is.

The explosion in the last shed that lifted the entire roof an inch or two in the air taught me a thing or two:

1. cleat down the roof with stout iron straps and long bolts, and
2. people make an awful big deal out of having eyebrows.

Regards,
Neil
I literally laughed out loud several times reading this. But I must take issue with point number 1 from your "Lessons Learned". LET THE PRESSURE ESCAPE! Remember the Wolfsschanze! Stupid meeting hut...

My Baby in action: