Blackening / darkening aluminum??

[lab-dad]

I need to slightly darken the aluminum pulleys on my drill press.
Everything I have has failed me.
The chemicals i have do darken bur also pit.
I dont want them black but the polished finish is too bright.
Oils?
Goache?

Marty

[Mr Potato Head]

Go to your local industrial metal supply place they'll have the blackener you need, it's cheap too, a concentrated quart will last you a lifetime!
MPH

[Andi Little]

Didn't want to say anything for fear of getting it wrong! - But, have you tried "Oven cleaner"? Every time I've got any near ally' it has darkened it considerably, almost a deep gunmetal.

Just thinking.

[Design-HSB]

Hi Marty,

i think ALUMINUM-BLACKthe best way for your part.

[chester]

Marty, had some luck by using Muriatic acid and Hydrogen Peroxide 50/50. Not quite as potent on aluminum as most chemical etchants and can be weakened by using more peroxide.

[marc_reusser]

Pee? 

[finescalerr]

Okay, Marc. Your turn. Go stand in the corner. -- Russ

[lab-dad]

Marc,
Tried that - turned yellow..........

[chester]

A little off the subject but when I was young I would help my grandfather in his construction business. One Saturday I was given a can full of pee (donor unknown) and told to "paint" the galvanized gutters with it before the finish paint went on. I suspect the thought was it would etch the metal. I have no idea if this is so. I washed my hands thoroughly before lunch that day.

[lab-dad]

I have heard of the urine helping to promote the green on copper.

At this point i think I am going to leave the pulleys alone, they look pretty good "as-is".
May be just a hint of surface rust on the ones not used often, recently.......
It is coming along, pics soon.

-Marty

[shropshire lad]

Horse pee will blacken oak shavings , something to do with the ammonia in the pee . Though I suspect you will have to have some pretty potent pee to blacken aluminium .

  Do you want me to send you a pint or two of horse pee to have a bit of an experiment ? ! ? Or is your own toxic enough ?

   Nick

[chester]

It would be the ammonia if it were white oak. I built some wh. oak furniture that we tented and put ammonia gas into the tent to get a black color. Lye does a number on cherry too.

[eTraxx]

A while back I got a sample of InstaBlak A384. You can see from the pic this enough of a 'sample' to last me quite a while .. probably forever. The company shows a InstaBlak A385 also - http://www.epi.com/c/black-oxide/aluminum .. there is a button below each where you can request a sample. Might be worth the time.

[lab-dad]

Thanks Ed,
Dont use the regular (insta black) stuff on aluminum - pitted the hell out of the piece I did.
-Marty

[Malachi Constant]

For an alternative to the chemical treatments ... some acrylic glaze medium (Vallejo or craft store stuff) and a touch of deep gray acrylic paint.  Mixing the paint with glaze medium makes a transparent paint layer -- TINY touch of paint on the first round to check the effect ... let dry for several hours (takes a lot longer with glaze medium) ... go back with a slightly denser coat if needed.  And, for even more transparent coat ... touch of Vallejo black ink in glaze medium ... there won't be any opacity to the color, just a tinting effect like looking at it thru sunglasses.  -- Dallas