To brighten the discoloured glass-topped typewriter keys of this keyboard,
to make all keys have an even brightness and squeaky clean,
they were all removed from the machine,
and collected in plastic bags. In the bags there are then 49 typewriter key rings, 49 glass disks and more than 50 cardboard keytops.
To brighten the keyboard, all the individual parts of the keys were cleaned and new set of keytop labels were made to be placed over the top of the original cardboard keytop labels.
The re-touched, cleaned labels were then printed at the highest quality setting on a laser-printer. A fairly thin, smooth ivory-coloured paper was used. In hindsight a thicker paper (e.g. 120 grams) could possibly have been better - more opaque. Thin paper was used because of wanting to keep the original cardboard keytop labels on the typewriter, to fit on top without adding too much to the height of the stack held by the ring.
The nickelled brass rings had quite heavy corrosion. A rubbing with metal-polish did not have much effect - gently scrubbing with fine steel-wool was needed to clean them up. Pitting in some spots was made less noticeable by the aluminium-method.
The glass disks were all cleaned with soapy water, a wooden skewer was needed to scrape off the dirt-rings. The glass was surprisingly dirty, even in the disk-centres. After washing, the glass tops lost their yellowish hue and actually came out very bright and clean again.
Taking off the keys also confirmed that this is a Dutch machine that was modified with Norwegian characters. The 'new' keytops are of a different typeface, and also a smaller diameter, thinner card. The original card keytop was thinned-down to accommodate the new label on top when the machine was changed, probably back in 1937. For the other key, the thinning-down removed the lettering, so unknown what the original characters were for that one.
To create new inserts for the keys, the card keytop labels were scanned at 1200dpi resolution. This gives about 660 pixels across a label, enough for editing and decent quality printing. All the labels were then digitally cleaned. This was fairly straightforward by simply removing the label background and only keeping the black (very dark grey) marking. Never noticed it before, but it turned out that several letters have a tiny white dot in the lower-right of the character. Perhaps an aid to prevent accidentally reversing transparencies in the total printing/preparation process? (See e.g. the 'B' and the 'O' in below image.)
To protect the sintered toner, the printed sheet was given a coating of protective 'artists' varnish. This seals the toner, makes the surface smoother still and will help protect against moisture.
This varnish unfortunately also made the paper half-translucent, so that the original letter of the old label would show through underneath. Thicker paper maybe would have not had this problem... For this smooth, thin paper it was however solved by painting the reverse first with white paint and then a layer of grey paint. After experimenting on a blank bit of paper with different paints, a water-based acrylic modelling paint was used that did not warp the paper and also had excellent coverage.
These two extra layers on the bottom made the labels completely opaque, yet still thin and with a nice, smooth ivory finish on top. (One original 'M' label shown for comparison in the image above, next to it one new label upside-down showing the grey reverse. The labels are on a white background.)
The original colour of the tab (and backspace) key could still be seen where the label had been protected against fading by the ring. Because it is hard to predict colour when printed - several labels with different shades of red were added to the printed sheet. A simple, 100% red-toner turned out to be the cleanest and a good match for the machine.
The new, thin labels were fixed on top of the old labels with small dots of glue from a 'glue-stick' on the edges. This prevents rotation and also should allow them to come off again without any damage to the visible part of an old label - i.e. it is a reversible restoration. The new labels were placed in exactly the same orientation on the original, i.e. the same way 'up'. This was done to help in re-fitting of the cardboard to the key-bases.
Next a glass disk was placed on top and the stack 'fed' into a ring - given a firm push to fully seat it in the ring. For orientation, the cleanest, least-corroded part of a ring was chosen to be in front, to be in view.
Dots of glue were placed on the key-base, exactly as was done originally in the S&N factory. Every key-top stack was then pressed onto its key-base and the three tabs folded-over. The glue should prevent the labels from rotating. For most keys, the cardboard keytop label still had an impression of the key-base embossed, this made the cardboard 'fit' the base and will also make rotating unlikely.
The tabs of the key-rings are of course the weak element; brass does not like bending. Replacement key-rings are not so easily sourced today, so there'd be no easy way out in case of mishaps. Luckily, only one of the 147 tabs broke off - there were also two that started to crack, these were 'stabilised' with a spot of cyanoacrylate glue in the crack.
The overall outcome of the entire procedure is a cleaned, bright keyboard with the original graphics that does not look too 'new' or out of place. The original labels are still present on all keys, so in principle this is a reversible restoration.
This barn-find wreck-machine is starting to look very presentable - a very rewarding machine to try to fix-up :)
