Restoring Spark Plugs

[GG Gregory]

I have a descent sized spark plug collection that I plan on making as a display. My question is what’s the best coating to apply to stop the flash rust once they’ve been cleaned ? Would gun bluing work?? It would look more authentic if the bluing will stick to the metal.

[speedytinc]

I have a descent sized spark plug collection that I plan on making as a display. My question is what’s the best coating to apply to stop the flash rust once they’ve been cleaned ? Would gun bluing work?? It would look more authentic if the bluing will stick to the metal.

I have used gun bluing. Works well & looks correct. As in bluing gun parts, all metal must be very clean, no oil residue.

As far as correct finish: example - most bodies are smooth, polished or semi polished. You would need to prep the metal similarly.
A bead blasted, blued body will not look correct.

[Terry_007]

Nice to hear of another collector! I've been at it for nearly 50 years. Do you belong to the Spark Plug Collectors of America (SPCOA)? The club has a page on Facebook and a fantastic publication - "The Ignitor." The subject of restoration has come up numerous times and there are a lot of different techniques.

Everyone agrees there are a few things to be careful of - first and foremost -avoid the heavy course wire wheel! It'll do more damage than good. Using a wire wheel will peel off any original plating, it'll gouge the surface and leave awful marks. The wire wheel will also round edges and corners leaving big scars, and it can quickly remove any information marked or stamped into the plug body. Same for heavy-handed buffing. Many plug insulators were marked with logos and manufacturers names on them. Some were glazed to protect them but many others were simply rubber stamped or used a decal. A wire wheel will make them disappear in a heartbeat and can actually "burn" dark marks into the porcelain.

Best cleaning technique is 4-0 steel-wool with WD-40 and some elbow grease. Hand-held soft bristle wire brushes used gently can be used with some WD-40 to remove heavy rust and crud especially in threads.

Sometimes, disassembly of the plug is necessary to do a thorough and proper clean. Soaking in PB blaster for extended periods of time, even carefully applying a touch of heat will help. Another "never do" is try to clamp the plug in a vice to disassemble it. If your wrench slips you may break the insulator! Use two box end wrenches-one for the base and another for the gland or packing nut. Squeeze them together and you should be able to separate the steel parts to carefully remove the insulator. The WD-40 and steel wool again comes into play scrubbing the crud out of the base as well as cleaning the insulator (carefully). Avoid causing any harm to the info on the porcelain.

Enough of my restoration lecture - you said the plugs are ready to display and need to prevent rust. If you used gun blue to recolor them be aware that is a caustic substance and the plug will quickly rust over unless acids are neutralized. I actually spray mine down with Windex after bluing and wiping them off. The amonia in the Windex helps neutralize the acids. Let them soak a bit, then wipe down with a clean rag. Once dried use some of the 4-0 steel wool to lightly "buff" the steel. You want a dark gray finish for most.

For those that should be dark blue, or even a black color, you can skip the finish wipe with 4-0 steel wool and either wipe some 3-in-1 oil on it, or use a semi-gloss or satin clear varnish lightly sprayed on. Protect the insulator though. Some varnish will turn a yellowish color over time but that shouldn't show on dark colored steel parts. As an alternative to bluing, heat the steel and drop it into some used motor oil. It'll blacken the steel nicely. Don't do it in the kitchen though!

I could go on - but some photos of your collection and handiwork would be great to see.

Here is a photo of a recent discovery that I just cleaned for display.

[GG Gregory]

Wow Terry that’s a lot more information than I thought I’d get ! I wouldn’t consider myself a true plug collector, I inherited a bunch of antique used plugs and maybe a few unused ones, nearly all Model T. I collect a little of everything, and I’m running out of room ! Thanks for the info, I’ll check out that Facebook page for sure.

[Steve Jelf]

I used gun bluing on these. I think it looks pretty decent.

[GG Gregory]

Those look great Steve!

[Original Smith]

Are the copper gaskets for inside still available?

[Steve Jelf]

Are the copper gaskets for inside still available?

I was never able to find any, so I use copper crush gaskets. https://dauntlessgeezer.com/DG95.html