Thread: Everything You Ever Wanted To Know About Celluloid (but was afraid to find out...)

Originally Posted by Neil Miller

I guess I'm just getting old. And I don't like it.

Don't feel like the Lone Ranger .......... it beats the alternative ......... I guess .....

Originally Posted by JimmyHAD

Don't feel like the Lone Ranger .......... it beats the alternative ......... I guess .....

OK, kemosabe.

I found the reference to water and metal salts as agents of degradation interesting. Also the loss of camphor as a precursor of rot. I wonder if soaking scales in camphor would help "reverse" the process?

Neil, as a chemist, my perception may be colored more towards that perspective. I hadn't seen any threads on SRP explaining this scale rot phenomena in chemical terms, especially in a way I felt was suited for an average Joe without a background in chemistry, hence my enthusiasm in posting the article.

The article was written by a conservationist in a non-scientific journal who did good research into the chemistry of celluloid as it pertains to its decomposition and preservation, and I felt it had merit.

For example we all know "cell rot results from degassing...". Which is of course, a simplification. To some, the natural question resulting from this statement is, "What is this gas from Hell? Now I know not everyone who says they understand all about cell rot could answer the question correctly. But if they read the article, they'll learn that it's one of the decomposition products, the aqueous nitric acid (which only exists as a gas at very high temp, much higher than would ignite the celluloid) that causes the damage to the metal. Not the gaseous camphor, though this process is described as degassing.

I'm sure camphor came to be the standard solvent at the time simply as a result of the scientific process through experimentation. Solubility is often determined for a material through trial and error. I have used this simple method myself many times, with more success than one might think. It is absolutely standard procedure in a chemical synthesis laboratory. Polarity, reaction kinetics, ease of use, expense, many factors can determine what makes a solvent favorable. If you'd like, I'd be happy to do a literature review to try to find some more specific information about the actual processes specific to camphor as a solvent for cellulose nitrate.

As to why this sudden reaction begins (actually, it begins to reverse), it's all about the thermodynamics of the reaction and a factor called Activation Energy (which we chem nerds refer to as "E sub a"). Once this reaction specific amount of energy is applied to the reagents (whether thermal energy, mechanical energy, UV excitation, whatever it may be), the reaction will proceed at a rate dictated by it's kinetics. Which in the case of this reversed celluloid synthesis reaction, are actually pretty quick. We can see it overnight. But the kinetics can only start after the activation energy level required for the reaction is achieved.

I'd be happy to help address other questions you have about the chemical process of the synthesis of celluloid, I'd just ask that you only hit me with one at a time, as I may have to research a bit to be able to provide some interesting history behind the chemistry.

I understand your chagrin at some of the lower quality posts. As I grow older (I'm almost 49 now) I find myself increasingly intolerant as well. It's only with great restraint that I can step away from the keyboard. What you say is profound: "Without the urge to solve problems and work at something we are losing a valuable resource and witnessing the rise of a load of dunderheads". To which I would add "and the decline and death of Western Civilization".

Again I'm with you Neil, It's hell gettin' old.

With Respect (and a deep love for your strops),
Mike

Originally Posted by Splashone

I found the reference to water and metal salts as agents of degradation interesting. Also the loss of camphor as a precursor of rot. I wonder if soaking scales in camphor would help "reverse" the process?

Sadly, reversal is the problem! The reaction of the cellulose and nitric acid which created the celluloid is reversible. Once the decomposition has started, adding camphor in excess would be analogous to you're best buddy messing around with your girlfriend, so you go punch somebody else's girlfriend

It's unlikely that the additional camphor would push the reaction back in it's intended direction (due to entropy...HEY!), and certainly not in its refined state.

BUT! You have your thinking cap on, and I commend you for it!

Thanks Mike,

That has partially explained a few things to me.

What still mystifies me is what you are calling Activation Energy, and why some examples of celluloid reach the reversal stage before others, and why some are still showing no sign of reaching that stage.

I used to belong to a group who made their own sensitised collodion by nitrating cotton in a nitric acid rich mix of nitric acid and sulphuric acid (horrible stuff as I am sure you know - one in particular is given to sending out clouds of vapour that spills down the sides of the flask), washing it copiously and then dissolving it in a mix of alcohol and ether to which some added a little chloroform. This was flowed onto a plate of glass and the whole dunked in an aquaeous solution of silver salts whle still tacky, the silver mx charmingly referred to as 'lunar caustic'. The mixes we used went back to the dawn of wetplate photography, which predated the marketable early varieties of celluloid/parkesine, and which shared many of the processes.

In the recipe books of the time we have instructions for using the purest grade chemicals, which makes me wonder just how pure they were, particularly as the advice on obtaining clean water was to scoop it up from a puddle after it had rained for some time. Apart from that there were the effects of different level of nitration, which is determined by the strength of the acid and is of the formost importance in making gun-cotton. With those sort of amateurish attempts one can see that anything could have gone awry at any stage of the process, but for something like celluloid produced on a large-scale basis one would expect tighter quality control.

I know for instance that the stuff shrank a lot and I have seen a modern video of celluloid production, in Italy I think, where the sheets of celluloid were taken from the settling mould and stacked. This by sheer weight of pressure drove out a lot of fluid, and the stuff was turned and re-stacked for quite a long time (I forget how long now - definitely weeks, could have been months though) which got rid of the remaining free fluid and also allowed the material to shrink and become more dimensionally stable. How then did they incorporate metal mouldings and stampings like fancy razors into the scales? They look like they were placed in a mould and the celluloid mix injected on top, but then we would still have excess fluid in the celluloid and it would shrink a lot too, probably differentially at the junctions of the metal parts due to them having different rates of thermal expansion and contraction.

There is celluloid still in production in America - a lot of the knife-making companies sell it to make handle pieces and bolsters from, yet it no longer smells the same. There is not the merest hint of camphor (even back in the day though, camphor was not used for all types of celluloid, particularly the type that has an acetic acid or vinegary smell), instead it smells of the resin used to make glass reinforced plastic. I have queried this with one company, who assure me that the stuff is 100% celluloid - it looks like it, but I have my doubts.

There is a niche market for it in Japan too, so it is not gone the way of the dinosaurs yet. In fact some luthiers insist on having the real thing to repair old guitars and the like, so there are other markets for it besides knife-making. One suspects that it still finds use in some high grade fountain pens and is milled into shapes like shaving brush handles, etc.

With regard to cell rot, the characteristic patterning caused by mottled celluloids is well known, but this sort of 'pattern staining' is seen on blades that have mottled scales not made of celluloid. Such a phenomenon as pattern staining is well known in the building industry - one example would be patching up the eaves of a building with different materials like thermal blocks, wood, metal and bricks and putting a render coat of plaster over the whole thing. Because of the difference in thermal load of the different products under the render coat, the air in contact with the wall is warmer in some places, colder in others. Air holds moisture, and when the temperature goes below a certain level it dumps that moisture - hence the misting up of windows and dew-line faults in buidings. The opposite is true to - where it is warmer the air moves more, so there is less chance of dumping its load (dirt/dust/water). After a while we begin to see the shadow of the the different material under the render.

I suppose that the same sort of thing can happen to razors - the lighter parts of the scales will let the metal warm up beneath them, while the darker bits will absorb that energy and leave the metal under then cooler. When the temperature drops we get a smaller-scale 'pattern-staining' effect.
Does that affect celluloid scales that are breaking down? Is the leaching out of acid increased or delayed by this process? Is this why a controlled environment with no heat extremes is advised? Does keeping the items in the dark avoid the pattern-staining occurring in the first place by stopping the passage of light altogether?

Darker, opaque celluloid scales seem immune to this - is this the result of fillers, or the smaller ratio of cellulose as a lot of the weight of the scale is made up from fillers and colouring agents? Or is there another reason entirely?

That is the sort of stuff I thought I would have seen, as my viewpoint is from the restoration of razors. A bit like driving a car, really -I am not that interested in how the engine was composed of elemental particles and worked and bored, I just want to know where to stick the petrol, oil and water! That is a personal point of view, conflicting with many other peoples points of view, just like my point of view about celluloid conflicts with that of many other people. Either way, I don't care - we take what we want from something like these examples and then move on - it doesn't really matter, does it?! I couldn't take much - my loss.

Your explanations and clarifications are very elegant though, and it is a pleasure to read them. You are a very clever person and I'm glad to have met you, even if it is only over the ether (not the type used in collodion, I hasten to add!).

PS I am older than you, therefor I am grumpier! Bah! Humbug!

Regards,
Neil

Well, I got a lot out of this thread. I'm often slow on the uptake, but this explains why some of my scales smell like Vick's Vapor Rub and explains why I shouldn't waste time refurbishing them.

Originally Posted by Sandycrack

Well, I got a lot out of this thread. I'm often slow on the uptake, but this explains why some of my scales smell like Vick's Vapor Rub and explains why I shouldn't waste time refurbishing them.

I hate to flog a dead horse, but that has been said time after time in different threads on this forum too...

Regards,
Neil

Well La Tee Da! Thanks for taking the time Entropy in an attempt to add to the site.

Originally Posted by Neil Miller

I hate to flog a dead horse, but that has been said time after time in different threads on this forum too...

Regards,
Neil

It's your horse and you can flog him as often as you like.