Sunday, October 17, 2021

Cleaning the Comptometer Supertotalizer

The fur between the keys is removed and the overall machine polished-up nicely.

The keytops themselves were first cleaned of the runny 'goo' by simply wiping it off with tissue-paper. Much of the remaining dirt and expanded 'ink' was removed with a rag plus soap and water. The top surface and the sides of the octagonal keys was finally 'polished' with metal-polish - this makes the surface a little brighter again without damaging too much. Especially the white, dimpled (odd-numbered) keys have deteriorated - the old plastic has shrunk, cracked and curled up. The keytops are still not completely cleaned, but the keyboard is now serviceable and no longer 'icky' to touch.

To clean between the keys without removing them (a non-trivial procedure), a 1/4" square wooden slat wrapped in a damp rag was used to get between the stems. This slat with cotton rag with some metal-polish was next used to clean the stems themselves. Great care was taken to not rub the top-plate with the metal-polish, as this would have damaged the finish!

The case of the Comptometer is made of copper-plated steel that was then given a clear lacquer top-coat. On the front-right corner these layers are worn-through from regular use. (Quite some information about these Comptometers is on the internet at various sites, for example a lot of information on the different types and on the mechanism is on John Wolff's Web Museum site.)

The copper-coloured case was washed overall with a damp cloth with soapy water. With a wooden toothpick the dirt around the edges of the raised decorations was cleaned off.

Most of the dark stains are corrosion and/or dirt of the copper underneath the lacquer. For example; most of the dark spots on the top-plate between the stems clearly show the hole in the lacquer, with surrounding discolouring.

This means that many of the stains and spots cannot be cleaned without completely destroying the finish. These machines were never brightly copper-coloured, but always a darker brown. (Perhaps the finish was chosen to mimic the original wooden box models in general appearance, when they switched to metal cases in 1904. Pure speculation, but could well be.)

Nevertheless, the machine cleans up well. To protect the finish against future corrosion damage from cracks in the lacquer, the case was given a polish with petroleum jelly (Vaseline). This will fill cracks and help seal the metal from oxygen - plus it gives a bit of a shine to the surface.

The serial numbers of the machine are repeated on the mechanism internally. These are the same as those stamped on the outer case, further confirming the calculator is 'unmolested' and original.

On Comptometer model J calculators the back plate generally carries a list of patents. On the Supertotalizer the backplate only has the Comptometer script-logo and the patent list is now on the bottom-plate of the machine.

On this machine the list is scratched and a bit difficult to read. Even though this machine was manufactured around 1935, the list still starts with Dorr E. Felt's first US patent 366,945 for the Comptometer issued in 1887.

The display windows have strips of celluloid behind them. The celluloid is of course yellowed with age, but not too bad. Several yellowed-dot patterns on the sheets were evidence that these strips had been shifted around several times to place a new, bright bit of celluloid in front of the windows. The strips were merely cleaned and placed back.

Next to tackle the mechanism. The columns 2 to 5 work, the rest refuse to budge or will not do a carry at all. It's as if the machine is lubricated with treacle. The Totalizer bits are worse, as if lubricated by tar.

Nevertheless, the mechanism is complete with no obvious damage so it should respond well to new oil and exercise! Lots of exercise :-)

No comments:

Post a Comment