How do you keep brass shiny without having to polish it?
Here is my situation. Many of you will recall my work on my
McKeen Motor Car:
I have encountered a problem with the brass window frames in that they are tarnishing. My question is what should I have done to prevent that from happening?
FYI, the window frames were cut from 1/4" brass tube and they were clear coated after installation. Should I have etched them before installing and clear coating them, and what should I have used to etch them? Would vinegar have worked?
Dave, it’s likely that the cut edges of the tubing began to oxidise about 3 seconds after you completed each cut, although by the time that you sprayed them, they probably still looked pretty good. You wouldn’t have noticed the oxidation until later. I’d think that the clear coat might have protected them if it had been applied right after cutting each piece, but that would be a miserable and time-consuming procedure.
I can’t see that etching them would prevent tarnishing…it might strip-off minor tarnishing that had already occurred, but as soon as it’s bare, it’s exposed and begins to oxidise. Even handling brass sheet can result in the surface later developing the handler’s fingerprints.
I’d guess it to be difficult to remove those window frames with messing up other stuff around them.
If you have a steady hand, you might be able to paint them with brass-coloured paint.
Hi Dave. That car is the coolest thing… The stickiest material I know is shellac. Diluted, it can be brushed on and would probably prevent tarnishing. Of course, it can be painted over for extra protection…
The problem is that the irregular tarnish is occurring in a place that is difficult to address. I lived in a 1919 house full of brass fixtures and plates, all of which I carefully polished. In no case did I succeed in clearcoating that produced a finish that went on without distortion of the surface finish or dulling of the ‘shine’ that also kept parts of the surface from discoloring after a few years. At the time (this was near New York in the years before EPA, when silver tarnished in six weeks) the advice was not to coat at all and just keep up on the polishing.
Oddly enough, he might be able to make a polishing jig for the portholes that would selectively polish and shine those tube edges, with a pilot on the end fitting the bore of the tubing to guide and align it. He might have to come back from the inside with a little black paint inside the ‘rings’ and it would be a little tedious to go down both sides, but it beats trying to paint a smooth regular ring on just the edges…
Now at some point he’s going to want to put glazing in those portholes. And what I’d do is make up a removable clear strip per side, with the portholes done in clear microscope cover glass and attached carefully to the strip so the whole shebang comes out as a piece when it’s time to ‘do’ the brass edges.
If i were tortured into saying a coating product, it would be thinned marine spar varnish.
Technically you would want to gleam those rims, to the same full polish as the original porthole frames likely were. Making a burnish tip for the rotary type of device might be easy – and might let you keep a beaded edge on the portholes without messing up the paint.
Normal weathering on those frames would likely appear the usual slightly-reddish brown, unless you ‘operate’ the car in a marine environment
If I’m not mistaken, Dave did glaze those portholes, too, although I don’t know if it was with glass or plastic. I seem to recall offering to punch-out clear plastic discs, but my punch selection (meant for sheet metal) either didn’t have the needed size or had a point at the centre of the punch, which would have made a dimple on the “glass”. Most of the punches had had the pointy bit removed before I got them…
I did try to glaze the round windows but it didn’t work out. Wayne did offer to use his punch set to make the proper sized glazing out of acrylic sheet. I was able to punch windows out using a straight punch but the windows jammed in the punch and any attempt to remove them caused damage. I did use microscope slide glass from Ngineering for the square windows and that worked out great.
It tried to use round glass microscope slide covers but I couldn’t find the exact size covers to fit the frames. The ones that were slightly smaller left a messy glue joint between the glass and the brass. The ones that were too large wouldn’t fit flush against the inside of the frame because of irregularities in the resin shell immediately beside the window openings. The Funaro and Camerlengo shell was nicely finished on the outside but the interior was not. Among other things, the walls were too thick and grinding them down to create a perfectly smooth finish proved to be beyond my capabilities. Had I been able to do that, Overmod’s suggestion about how to make a glazing system might have worked.
The other thing that dissuaded from trying to glaze the round portholes is that I couldn’t figure out how to get the glass lined up so that the reflection angle would be identical. I figured that if the windows reflected at different angles the effect would not look very good. This is why I declined doctorwayne’s offer to try to punch out windows from acrylic sheet. Again, Overmod’s suggestion might solve this problem.
The reason I am asking the question is that a fellow forum member is in the process of scratchbuilding a McKeen car for an NMRA Challenge. He is at the stage where he needs to figure out how to do the round window frames, and I wanted to try to help him avoid the tarnishing issue.
What he needs to do is make up a small dap or dop stick that will hold a piece of cover glass as though it were a gemstone being faceted. That will let him work it against something like a diamond disk in a mandrel in a clamped Dremel until the glass is precisely circular.
I have not fully worked through the best way to get all the little glass pieces aligned precisely and also depthed precisely so they both line up with the prototype window frame and appear aligned with each other as he wants (I would check to see just how precise McKeen portholes actually were – they might not have been as precise as Budd streamliner windows!). Fallback is to use multiple thicknesses of cover glass cemented together to make the thickness, but unless glued before grinding to shape it might be tedious…
The portholes on my Funaro and Camerlengo shell needed to be drilled out a bit. There was lots of flash, but drilling them made them all exactly the same size so the 1/4" brass tube fit very nicely. As I mentioned before, the biggest problem was that the car sides were too thick and the inside was uneven. There was also a huge issue with the inside of the roof. It was full of resin right to the tops of the windows. It took a long time to grind all of that excess material out.
The person who is building a McKeen car from scratch has already made the shell using 3D printing. I don’t know how thick the walls are but I assume that the insides should be relatively straight and uniform. I’ll refer him to this thread if he hasn’t seen it already. There have been lots of good ideas that are worth him considering. However, I’m not sure we have fully addressed the brass tarnishing prevention options.
I would cheat – get a cheap jewelry electroplate outfit and plate the burnished edges of the tube pieces as they are finished. Even in precious metal that’s a small amount of material…
I would cheat – get a cheap jewelry electroplate outfit and plate the burnished edges of the tube pieces as they are finished. Even in precious metal that’s a small amount of material…
You might even be able to use that approach on your car if there is a way to put the counterelectrode on the back of the tube inside the shell.
I don’t see how that would be cheating. If it works, then it works!
I am contemplating trying to remove the window frames. I can’t remember what I used to glue them into place but the bonding surface is very small so they just might pop out without too much fuss. If they don’t come out straight that won’t be a problem because I would be more inclined to make new ones than try to preserve the old. I’m going to look at getting a plating machine. I have no ideal what they cost.
Dave
Edit:
Buying my own plating machine would be prohibitively expensive. There are local plating companies that can do the job for much less. If I was doing it every day then buying one might be more economical, but the fact is that the need to plate something won’t come up very often.
I am just wondering if you could use a piece of the same brass tubing as you used for the framing of the portholes, to stamp-out “glass” from clear .005" sheet styrene. Because it would contact only the material from which the windows are punched, not the actual window itself, there’s be no scratches on the “glass”.
That, of course, doesn’t address the tarnish issue…I wonder how difficult it would be to cover the brass window frames with gold foil?
Keep in mind that what I’m talking about is essentially a fancy pen that uses the plating material as the ‘nib’, and the electrolyte applied with a needle tip or just wicked or squirted to the contact patch. It’s used to ‘paint’ metals or reduction colors on the surface of jewelry pieces, and you could probably make one up with a cheap low-voltage high-current supply using only odds and ends of structural material if you didn’t want to buy one new.
There would be no need to remove the tubes from the side, which probably won’t happen without spoiling the paint. Everything I’ve suggested hinges on the idea of polishing, burnishing, plating, etc. with the tube installed, and without damaging or loosening them or fouling anything up that cannot be field-polished or renewed.
I am not sure that the Sharpie ‘ink’ has particles that are small enough not to be visible in the produced surface finish. One thing is that the surface tension of the relatively thick bead the pen will draw will create the effect of a half-round porthole frame on the end of the tube, a thoroughly desirable effect…
In my opinion the way to do Wayne’s method is to take a piece of your tubing and cut a long bevel on the outside of the circumference, e.g. by chucking it in a drill and filing or stoning a long taper on the outside. This creates a sharp-edged ‘punch’ but I wouldn’t use it as a punch; I’d spin it and then press against the thin window material to cut a straight-sided plug without distortion. A piece of wire would push this out of the tube from the back if it stuck after cutting.
I think I am going to leave the windows open and pretend that it is a hot day. Assuming that I could cut the acrylic using your method, that still leaves the challenge of installing them without smearing glue all over the place. One of the other challenges which I just realized is that there are individual LEDs between each of the windows so I would have to work around those as well.
I just ordered a gold fine tip oil based Sharpie to give that a go.
I wasn’t kidding about using gold foil, Dave, and I wasn’t referring to gold-coloured foil, either. There’s some available HERE.
I think that it might work if you could cut it into strips just slightly narrower than the total circumference of the depth and thickness of your brass porthole frames. It would also need to be long enough to completely cover the inside circumference of the tubing slices.
Slip a piece of foil into the slice of tubing, centering the tubing on the width of the foil, then carefully fold the foil over the cut-edges of the tubing, then wrap the remainder of the foil over the outer circumference of the sliver of tubing - this should result in a slight gap on the outer circumference between the wrapped-around foil - apply a little ca at the gap to hold the foil in place.
It sounds like it might be kinda fiddly-work, but I watch a documentary where gold foil was being used to decorate antique furniture, and was surprised at how well it conforms to multiple contours and shapes, even without use of glues.
I didn’t think that you were kidding, but I cab’t see how I could apply it to my existing model without removing the window frames from the shell. I don’t think that I will go there.
However, I will pass on your suggestion to Rob who is the person scratchbuilding a McKeen car. I had already suggested that he explore having the window frames plated, but the foil raises another possibility.
