In restoration articles, we usually see blue hands hovering over an alcohol lamp in a neat little box of metal chips, with the steel gradually turning that deep, rich blue. It’s a bit like picking a mushroom in the forest. Easy! But how do you get to that forest – or grow your own mushrooms? That’s the part we’ll focus on.
So, we have a rare and valuable pocket watch, but the hands are far from decent – all corroded and dull. The goal is quite simple: we want classic blue hands, just like the ones we see in the catalogue.
In this review, we’ll pay special attention to the polishing process and how to keep the fragile hands secure while we work. We’ll also be keeping a running time log – and let’s note right away that the most time-consuming part is cleaning the hands properly, which is absolutely crucial to achieve an even, consistent colour.
FIXTURE
To avoid damaging the tiny parts during polishing, they must be securely fixed to a stable surface. Each hand should absolutely not deform or come loose from its holder.
To produce a series of new parts, custom-machined metal jigs/holders are typically used by manufacturers. But for a quick restoration job in the workshop, we’ll be using something a bit more humble – simple lollipop sticks.
For the hour hand, we’ll drill a hole in the stick to fit the hub snugly, so the hand sits firmly in place.
Double-sided tape will keep the body of the hand secure, but the hub should be the main thing holding it in place.
So, we’ve fixed the hour hand thanks to the hole. We won’t be able to do the same with the minute hand, though, as it doesn’t have the tube part. We’ll drill a smaller hole in the lollipop stick, and attach a toothpick to it using super glue. Then we’ll put the hand on. The base should be held tightly in place by the toothpick, and we’ll fix the body using double tape.
Now our hands shouldn’t break or come loose during the polishing process. We’ll apply force strictly parallel to the hand – from the base to the tip (left to right).
TIME: Securing the hands took 6 minutes
POLISHING
Our absolute goal is to keep the measurements and surface of the hand exactly the same after polishing. When manufacturing brand new parts, the blank part is always slightly thicker (by 20 microns or more) to account for polishing, but in our case, the hands are from 80 years ago. We won’t be able to replace this part in the case that it’s damaged or over-polished, so keeping the original size and proportions is critical.
For polishing we’ll use 2 types of abrasives:
- Lapping film (4500 grit) glued to a lollipop stick – for rust removal
- Orange Luxor paste on a soft rotary brush – for high lustre
The first polish, or, to be exact, removal of the top layer of rust, is completed with 4500 grit Lapping Film. We make sure the hand keeps its original flat or rounded areas, but also keep the edges sharp.
It is crucial to clean the hand with a naphtha soaked cotton bud after using the 4500 lapping film to remove the coarse grain from the abrasive. Finally we polish it using the rotary brush with the Luxor paste.
Step two is using a brush with some polishing paste to achieve a mirror finish.
If polishing reveals a deep rusted cavity, avoid applying too much pressure with the rotary tool. It’s better to go back to step one – use the 4500 grit abrasive to re-establish a clean, even surface with an even white sheen. Use coarser abrasive for deeper grinding if needed (1800 then 4500 grit).
TIME: Polishing took 15 minutes per cycle
(in reality, we had to polish and clean parts twice - the first attempt gave us a rather dull colour due to overheating)
CLEANING
The cleaning part is very important, we need to check the cleanliness of the parts after each stage. A contaminated rotary brush with coarse abrasive particles from the previous polishing stage can lead to tiny visible scratches and an uneven surface.
A crucial step after all polishing is to thoroughly cleanse the parts. We could use cotton buds and naphtha, but do it gently. You must not apply any pressure – cotton can leave scratches on the steel parts’ mirror surface.
| Cleaning stages (each hand must be cleansed individually, so that they don’t scratch each other) |
| 1. Jar with acetone – 3 minutes in ultrasonic machine (facing upwards) |
| 2. First rinse in naphtha – 2 minutes in ultrasonic machine (facing upwards) |
| 3. Second rinse in clean naphtha or Essence of Renata (facing upwards) |
| 4. Drying face-down on tissue paper, which allows the paper to absorb the fluid |
| 5. Air blow-drying |
| 6. Check that the surface is clean and shiny. If the liquid left any stains – drying was done incorrectly, go back to step 2. |
The clean hands should only be picked up using (clean!) wooden tweezers by their edges or foot. Nothing should ever come in contact with the polished surface.
TIME: Cleaning took 20 minutes
BLUING
Now, bluing the steel hands is a relatively well-known process, so we won’t focus too much on this stage. In our case we used an automatic enamel oven, because our other small oven just had to break. The target temperature is 279°C. The hands are inside a small hand-folded stainless steel box (you can also use thick copper foil) to prevent the edges from overheating.
There is a thermal insulating block between the heat spirals and metal box so that there’s no direct infrared rays touching the parts and potentially overheating them. Exposure time is 5-6 mins. If we left the hands in for remarkably longer, they’d get covered with dark oxidation spots.
Brief troubleshooting
| Remarkable stains / spots | Cleansing stage not completed thoroughly enough after polishing. Parts not handled correctly – only pick up the hands by their edges and only use a clean pair of wooden tweezers (re-sharpen tweezers fresh). |
| Uneven colour, lighter blue areas along edges | Your part may be overheating at edges, or heated unevenly. Protect it from direct heater infrared radiation. |
| Small stains all over the surface | You should not keep parts in the oven for more than 5-6 minutes. The solvent at the rinsing stage was not clean enough. |
| The steel didn’t turn blue, why? | You might be working with stainless steel. Use some magnet to check. |
If hands were cleansed and blued correctly, this is the kind of result you’d expect. However, something is still missing – the minute hand should have a mirror surface at the base.
TIME: Bluing took 12 minutes
FINISHING
Using a final lollipop stick, we should cover the main surface of the hand with yellow protection tape and only expose the surface that needs polishing.
We’re polishing it using lapping films glued to glass. First, 8000 grit (the pink film), then 14000 (yellow-green film), and another touch-up with 100000 (white film). In the end we get a clean mirror surface keeping natural blue around the edges.
TIME: Finishing took 3 minutes
QUALITY LEVEL
The quality standard for brand new modern parts is a bit higher, but there is a difference in the way the parts are manufactured. When producing new parts a 20-50 micron thickness difference is left to account for polishing. Vintage parts don’t have this kind of extra thickness, so the restoration quality is just not the same as for brand new parts, and this is completely normal.
More details about this KM Stowa watch is on our Shop page.
