The hands on my Vienna Concordia were a bit rusty. They had been blued originally, but just with rough edges and covered in scratches from the milled steel sheet. So thought I would polish them properly and try bluing them.
So I did a quick test with a heat gun to see if that would work. Firstly on some screws, that was easy. The minute hand was also easy but pretty uneven. I had some brass wool so tried that to even out the heat. It worked reasonably well. The hour hand in the photo even though it looks polished was still a long way off from a perfect surface. Still about 4 more hours of sanding.
I sanded the hands starting with 800 wet and dry, then 1000, 1200, 1500, 2000, 2500, 3000 and finally 5000. Then some Brasso. Cleaned with detergent and finishing off with acetone, trying extremely hard to not touch the metal which is absolutely critical.
There were a few minor scratches on one hand looking through a Peak scale 10x loupe, use a magnifying glass of some description, so decided to go back to 1500 wet and dry and repeat. I was not happy as it was going to be another 3 hours. In the end I am glad I redid the sanding and polishing, as even the tiniest scratch ruins the finished result.
The bluing is not perfect by any means, but considering the minute hand is 130mm long and varying widths of steel which was difficult to control the rate of heating, I think it is a pretty good effort. The bluing differences show up more in the photos than in real life. So I will live with it.
Key things I have learnt on this first go at bluing is next time I would use a brass shavings bed and a thick base of metal to even out the heat a lot more. Precook the shavings to burn off any impurities or dust.
The heat gun was a Bosch which goes up to 630°C accordingly to the LCD display. I used it at 630°C but on the lower speed fan. There was more than enough heat.
Using a heat gun as it blows air I would vacuum the room better than I did as it does blow dust around, you do not want any dust on the polished surface. Maybe better to set up in a bathroom as it is an easier space to remove dust and clear the room of towels and any other dust sources. It is that critical.
I think I would also use some 7000 wet and dry after the 5000, I was just getting a bit stingy buying this far more expensive paper.
So you can see the bluing process changing colour you need an area light (defused) so you would see the light as if the hands were a mirror, which they should be! So if looking at the hand almost square on, then the light should be the same angle to be seen in the reflection. A white translucent shopping bag over the light will do to defuse light. I had a desk light but it was not good enough as is. Also used a torch but because it is a point light source it didn't really help seeing the changing colour easily.
So final notes, polish out every last scratch, it took me 2 days. Clean clock hands and room as if doing heart surgery. With tweezers drop hands is motor oil straight after bluing to cool. I used some 10W-30
The dark blue photo is with point lighting and the light blue hands is with a small area light. I did also polish the back of the hands as it was often easier to sandwich the hand inside a folded piece of wet and dry when I couldn't sand anymore on one side as my fingers were a bit raw.
So I did a quick test with a heat gun to see if that would work. Firstly on some screws, that was easy. The minute hand was also easy but pretty uneven. I had some brass wool so tried that to even out the heat. It worked reasonably well. The hour hand in the photo even though it looks polished was still a long way off from a perfect surface. Still about 4 more hours of sanding.
I sanded the hands starting with 800 wet and dry, then 1000, 1200, 1500, 2000, 2500, 3000 and finally 5000. Then some Brasso. Cleaned with detergent and finishing off with acetone, trying extremely hard to not touch the metal which is absolutely critical.
There were a few minor scratches on one hand looking through a Peak scale 10x loupe, use a magnifying glass of some description, so decided to go back to 1500 wet and dry and repeat. I was not happy as it was going to be another 3 hours. In the end I am glad I redid the sanding and polishing, as even the tiniest scratch ruins the finished result.
The bluing is not perfect by any means, but considering the minute hand is 130mm long and varying widths of steel which was difficult to control the rate of heating, I think it is a pretty good effort. The bluing differences show up more in the photos than in real life. So I will live with it.
Key things I have learnt on this first go at bluing is next time I would use a brass shavings bed and a thick base of metal to even out the heat a lot more. Precook the shavings to burn off any impurities or dust.
The heat gun was a Bosch which goes up to 630°C accordingly to the LCD display. I used it at 630°C but on the lower speed fan. There was more than enough heat.
Using a heat gun as it blows air I would vacuum the room better than I did as it does blow dust around, you do not want any dust on the polished surface. Maybe better to set up in a bathroom as it is an easier space to remove dust and clear the room of towels and any other dust sources. It is that critical.
I think I would also use some 7000 wet and dry after the 5000, I was just getting a bit stingy buying this far more expensive paper.
So you can see the bluing process changing colour you need an area light (defused) so you would see the light as if the hands were a mirror, which they should be! So if looking at the hand almost square on, then the light should be the same angle to be seen in the reflection. A white translucent shopping bag over the light will do to defuse light. I had a desk light but it was not good enough as is. Also used a torch but because it is a point light source it didn't really help seeing the changing colour easily.
So final notes, polish out every last scratch, it took me 2 days. Clean clock hands and room as if doing heart surgery. With tweezers drop hands is motor oil straight after bluing to cool. I used some 10W-30
The dark blue photo is with point lighting and the light blue hands is with a small area light. I did also polish the back of the hands as it was often easier to sandwich the hand inside a folded piece of wet and dry when I couldn't sand anymore on one side as my fingers were a bit raw.
