Auto polishing compound on brass?

[OldEastRR]

For rolling stock, not a loco. Better to hand rub or use a felt buffing pad like on a Dreml? This is to prepare for an airbrush painting.

[peteski]

For painting brass you should not be smoothing (polishing) the surface.  You should try making it rougher to give the paint or primer a surface to "bite" into. Sandblasting with fine grit works really well, or etching the surface works too.

[TrainCat2]

Mr Metal Primer Spray #B504

[OldEastRR]

OK, the best way to clean off the tarnish, esp in hard to reach areas?

[Maletrain]

A couple of thoughts:

1.  Soak in vinegar to chemically remove tarnish

2.  Use an "air eraser" with baking soda to physically blast it away.

[peteski]

Regular white vinegar is only 2 or 5% solution of acetic acid.  It takes a long time for it to do its job.  I found a 25% concentrated vinegar in a German Deli. It is imported from Germany.  That stuff works quicker.

[John]

Regular white vinegar is only 2 or 5% solution of acetic acid.  It takes a long time for it to do its job.  I found a 25% concentrated vinegar in a German Deli. It is imported from Germany.  That stuff works quicker.

We used to put pennies in vinegar (back when they were still copper) -- made them "mint" shinny

[rodsup9000]

 The orange big box store in my area sells "cleaning vinegar" that's 20% acid for about $10 a gallon.   Might try some of that.

 It's in the isle with the cleaning supplies.

[garethashenden]

A lot of brass models are painted gold or lacquered clear from the factory. If the one you have is raw brass, I've had good luck with cleaning products such as Bar Keeper's Friend. Use it with an old toothbrush and it does a good job at removing tarnish.

[OldEastRR]

The car is an old Quality Craft kit of brass structure pieces (including grabs) with a few pewter parts for the cupola and platform details. I soldered all the brass together, expoxied the pewter parts, built a new (removable) plastic underbody to replace the wooden one. No varnish or any coating was applied to the brass. I will have to find a very small brush to clean the ends of the car behind the collision posts, brakewheel, etc.
Never heard of 20-25% acid vinegar. What is it used to clean? (I assume not just brass train models)

[peteski]

Never heard of 20-25% acid vinegar. What is it used to clean? (I assume not just brass train models)

The one I mentioned, is for human consumption (after diluting  it first of course). It's a vinegar concentrate.  I bought it because I saw it in the deli store and I figured that I would find it useful in hobby applications.

[Chris333]

Isn't 30% vinegar the type you find in a store for food?  I remember looking for 100% to kill weeds.

[Iain]

for pickling brass i use a mix of white vinegar and hydrodgen peroxide to make peracetic acid.

[peteski]

Isn't 30% vinegar the type you find in a store for food?  I remember looking for 100% to kill weeds.

No, the edible stuff in supermarkets is only a 5% solution.

[thomasjmdavis]

Isn't 30% vinegar the type you find in a store for food?  I remember looking for 100% to kill weeds.

Nope, not usually.  You will find it in some stores (or imported, as Peteski did) for the folks who dilute it to a given strength when pickling pickles, or other vegetables, or eggs or pigs feet or what have you.  You would not want 30% vinegar on your salad, it would take the finish off the salad bowl.  The standard white vinegar and apple cider  we get from the local food store is 5%.  In the cleaning aisle, they sell a version that is 8%.  At 30%, you really don't want to get it on your skin, or you will get pickled, too.

Note- way back in olden times, I was taught to soak brass parts treated in vinegar or other acidic solutions in a bath of baking soda and water, to neutralize the acid. I don't know if it is actually necessary, but I've always done it.  My recollection is that the reasons were to prevent any 'etching' of the metal by residual acid, and to prevent any contamination of paint.  I will leave it to the chemists here to weigh in on whether that makes sense, but so I was advised in the 1960s, and I've stuck with it.