How to get to the right finish for bluing

[Bernhard]

Hey guys!
I restored and reblued a rusty Luger a half year ago.
Grinded it down with sandpaper and made the finish with 180 grain size (i hope thats the right word for it).
My problem is that i didn't like the look of this surface that is made out of scratches, if you know what i mean.
I wondered how i get to a matt look ofter bluing it. Just like a modern Cz75 Pistol for example.
Sandblasting i think would be too rough, isn't it?
Is glasspearl blasting or with nutshells an option?
Would be interresting which options you know...

[G.T.]

Hi Bernhard, you have more to do! You stopped to early? After the 180 grit, or even 150 grit, you go to the next successive higher grit number in increments of 100, or less, maybe 80? Use a closed grit paper (3M Wet/Dry works for me) so random grains don't come loose and re-scratch the surface you just sanded? Example, start with 180, then got to 220, then 320, usually this is enough, and finish with a fine blending cloth. Originally it was all done, from machining to high polish finish, on grit charged cloth wheels...
The rule of thumb is sand with the next size grit until you can't see the lines from the previous grit? Then the next, and the next, so on and so on... The trick is removing the blemishes, and still keep all the lines sharp and the flat surfaces flat! Light is important, check your work often in bright sunlight... there is no substitute for that?
Good luck is needed as well, and I can offer plenty of that! The rest is up to you... best, til....lat'r.....GT

[Bernhard]

But that would end in a kind of polished surface and not a matt bluing.
I think grinding with sandpaper will not bring the result that i expect. I don't want a shiny mirror pistol.

[G.T.]

They offer different grades of glass beads, and also sodium bicarbonate is what some of the artse fartse artists use?..Or, you might look in to chemical etching acids and such... uncharted territory there... You'd pretty much be on your own... Good Luck, til....lat'r....GT

[DonVoigt]

I have found that a fine wire wheel is about a close as one can get to the original, military
semi-matte finish.

180 grit is way too coarse, and looks just as you describe-scratchy!
I would go to 320 and if you don't like that, use the wire wheel.

Finish prep changed over the years also on both military and commercial lugers.
If you will tell us what make and model luger you have, perhaps someone can post a picture of one in original livery.

[calibrator]

I glass bead a LOT of parts for restoration of vintage Mercedes Gullwings and Roadsters.

Line pressure is the key (as well as grit size/material of course). It's most noticeable with aluminum castings. ~ 40 psi seems to give a nice smooth satin-like look. 120 psi gives it a shot peened appearance (not bad in some cases, but NOT for a $1M investor car). At high pressure (over 100 psi) small parts, especially sheet metal will bend, warp and twist.

Also found that when polishing plastics/acrylics, a final pass with carnuba wax gives it a boost.

YMMV

[Heinz]

If you are using an authentic rust blue finish the rusting will impart a very slight matting to the surface. Very characteristic of that original style finish.

[Edward Tinker]

I was trying my hand at sanding a very pitted byf years ago - I had gotten to the point of very high sanding paper 600 or 800 and was told that if it was too shiny, it'd look like a mirror finish, which is pretty, but very un-luger like....

[Bernhard]

@Edward:
Exactly. I want i to look smooth but matt and not shiny.

@Calibrator:
Yeah. I think that sand blasting is too rough.
Bead blasting is maybe the key.
Would be interresting how metall surfaces appear after bead blasting and bluing it....

[grantman]

You might want to try soda blasting. This is used on soft brick in house restorations. I have soda blasted mild steel and it gives a soft satin finish.

[4 Scale]

I recall seeing a refinished pistol a few years back where the owner said he had used 220 grit to get the surface right. As I recall it did look about right. Good luck and please post photos when you're done.

[G.T.]

The key to this whole thread is flat & sharp! Meaning surfaces and corners... The end result, whether shiny or dull, is going to look either great, or like sh**t if the edges are round and the flats wavy???
If you look on the internet, there are degrees of finish documented that go from high polish to flat. I think the info stating 220 W/D or there about is probably as close as you can get by hand, and the final prep, whether it be a charged wheel, tumbling, or blasting is a matter of choice and trial and error... .... Lot'sa effort, and most certainly a quest.... best to all, til....lat'r.....GT

[lugerholsterrepair]

Bead blasting is maybe the key.
Would be interesting how metal surfaces appear after bead blasting and bluing it....


Glass bead blasting is a disappointing finish. Too dimpled. Soda would be something I would try.

[Heinz]

If you want the finish to look like the original, you will need to rust blue it like the factory originally did. Some of the later Lugers are dip blued, but the older ones are all rust blued. This requires 3 things. An appropriate blueing formula, careful hand finishing with abrasives, and a "pickle" of the metal before applying the browning solution. The rusting requires an application to a spotlessly clean pickled finish, allowing the rust to form, brushing the rust off, and then boiling the browned finish to convert to black. It usually takes at least 3 passes. Some folks are extremely good at this. There are no shortcuts. Bead blasting and cold blue will not get you there

Unless you are doing it yourself, it is probably too much work for a shooter. But the pickle and quick blue will give you a nice matt finish IF you have carefully prepared the surface.

[Lugerdoc]

In the past, I've had a few cheap shooters bead blasted and dip blued. They come out looking like a phospate (Parkerized) finish. TH