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Blacksmithing and Metallurgy

How to blacken steel [no paint]

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Old 11-10-2009, 11:00:50 PM
Beez Beez is offline
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Default How to blacken steel [no paint]

hi guys just want to know how to blacken steel without using paint, thanks for your help Beez
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Old 11-10-2009, 11:04:02 PM
Eric M. Eric M. is offline
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Default Re: How to blacken steel [no paint]

I had pretty good success by heating the part (take-apart spark plug base) a dull red and then quenching it in nasty old motor oil. Gave it a very nice dark color. Washed the oil residue off with ether and gasoline and it looks great.
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Old 11-11-2009, 01:57:14 AM
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ssimntih ssimntih is offline
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Default Re: How to blacken steel [no paint]

when you quench the part in the oil, make sure you cover the container immediately, one reason is it cools the steel that much slower, it also contains any chance of a very likely fire.
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Old 11-11-2009, 08:44:03 AM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: How to blacken steel [no paint]

Go to your local gun store and buy a bottle of gun blue. Ron
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Old 11-11-2009, 11:23:11 AM
PTSideshow PTSideshow is offline
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Default Re: How to blacken steel [no paint]

To blacken steel, with oil there are a lot of things that are on the net that are old BS passed down from the days the smith was next to a tar pit.

First: is DO NOT USE USED MOTOR OIL! In the last 25 years or so the material in the engines that the oil is used in are a lot of exotic stuff. Cadmium and all the other heavy type metals that wear away and are collected in the oil.

When you heat up and burn the oil the heavy metals can become airborne and you inhale them.

Second: there is no advantage to using used oil with the high carbon in it. You will not transfer more carbon to the surface skin of the metal. The heated oil layers a very thin coating of carbon on the surface.

Third: Don't use old oil as it might be a synthetic blended oil with the natural oils. The higher priced oils that are sold as specialty oils will say so the regular oils use it as an extender, to make the natural oil go longer therefore make a cheaper product.

Plus with all the additives that are in the oils, for this and that you have no idea what will be in the smoke and fumes you could be inhaling.

Fourth: This is simply a heat patina with an oil finish. And if that's the case, I would use Linseed oil over motor oil any day. After 500 degrees steel turns blue/black anyway. Dipping orange hot steel in oil will make it fairly brittle as well. I've used the linseed oil, or even other vegetable oils to get a blacken finish on forge work, with or without paraffin or bees wax. Depending on what kind of black you're looking for. The colors or depths of darkness can vary from brown through black.

In this English Art college text book. Here what was said about the linseed oil.

* It is less likely to burst into strong flame, like the other oils.
* Higher flash point or ignition point along with smoke point.
* If it does it can be put out easily .
* And yes at the orange heat or above the black heat range the idea, was I think from what I have read was to get carbon into the surface of the steel. But then you may have a problem with scale. It was liked by the wrought iron workers in England because it gave a good outdoor finish.

To coat it you have a number of options, be warned that this is an outside the shop exercise. Smoke, smell and more smoke!

Over a sand tray with the piece in the center using a torch. Then brush the linseed oil on with a natural bristle brush(hog bristle) rather than a synthetic one which would disappear! The same can be said if you wipe it on with rags and gloves over a sand tray. make sure the rags aren't synthetic as some of the material has a low melting point. Don't use the oven to heat the piece or reheat to give it a second coat. This can be very detrimental to your wallet. New stove oven and to your health and happiness!

Fifth: food use utensils the food grade oils with the peanut and canola oils having the highest smoke point temps. Than say a vegetable oil.

Whether it is for kitchen accessories, tools or anything in the house if you have little ones running around that put everything in their mouths do you want them sucking on heavy metals. Which are on the fireplace set?

You can think of it like seasoning a iron pan, you don't need to get it forging hot. You need to heat it up to open the pores if you will to accepts the oil carbon layer.

I have used the rag and wipe on method this works the best with straight simple items.

The natural bristles hog brushes work best for something with a lot of scroll and curlicues.

If it is a large involved item a weed burner and an oil type sprayer will work.

It is a false economy to think you are saving money by using the old motor oil, besides you can all was sneak some out of the kitchen or save the used fryer oil or some of it. But be aware using fryer oil does have it drawback the lingering smell attached to what you coat.

And finally if the item is given as a gift or sold at some point it will have to be reapplied or tell them to paste wax it every 6 months to a year. the heavier the use the more often. As in the old style ranch farm dinner triangle or gong.
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Old 12-08-2009, 09:41:25 AM
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Randy Hart Randy Hart is offline
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Default Re: How to blacken steel [no paint]

While at a living village / museum I was hanging around the black smith shop and asked what was used to get the nice dark color on their finished work. He smiled and said it was a secret.. Returning back several hours later I saw him rub a block of Bee's wax over the warmed tool. He looked up and smiled saying so much for my secret.

It works well for me and seems to hold off rust very well so far.
He who dies with the most STUFF wins!
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Old 12-23-2009, 06:41:42 AM
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Fred Van Hook Fred Van Hook is offline
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Default Re: How to blacken steel [no paint]

A friend of mine sent me this and he has had some very good results with it.

When I took blacksmithing class they said any hydrocarbon would work with the heat/oil method. It is the
cast-iron skillet seasoning method.

The bottle of liquid gun bluing from a department store will darken metal (including zinc plated screw
heads) but it's not a very deep black and can rub off easily. Ditto for a cold darkening product called,
"Tool Black."

Gunsmiths use a hot bath technique for a deep dark black-oxide finish. So do industrial tool mfgr.'s. It
is far and away the best (better than parkerizing especially if you want a polished surface). To purchase
the official chemicals will run you over $100.

Here is a dirt cheap recipe:
One can of "Drain Out" brand drain cleaner (1lb, 2oz) to one pint of water at 280-300F degrees for 15-20
minutes. Those were all of the instructions I found online and it works marvelously. I bought a can at
the local hardware store for $3.97 + tx.
Make sure you use the crystal type not the liquid...

Now the part of the story the article I read left out.

When you add the drain cleaner to the water two things happen: 1.) A violent chemical reaction takes
place bringing the water to a boil (212F). If you add the stuff too quickly in a shallow pan, it can boil
over. And 2.) It releases toxic fumes which may include ammonia gas which is lethal.

Do that part outside. Once the chemical reaction settles down, it quits releasing fumes and it's safe to
take in the house and blacken parts on the stove. Hang them by iron wire.

But it's only safe if you have a brain. After boiling for a while, the level went down to where my parts
were exposed. So I thought, "I'll add water." Water boils at 212F, and my bath was at 300F. Imagine
pouring cold water into a deep fat fryer: Instant eruption.

Additiona Info:

Any drain cleaner that includes lye and nitrates should work. Homemade concoctions using ammonia nitrate
fertilizer or potassium nitrate call for 2 parts lye to 1 part nitrate. A pound and a quarter of that
mixture per pint of water.

One other thing that seems kind of important: Temperature.

Most cooking thermometers only go up to 220 degrees. I used an infrared dealy-bob. If you try using one of
those aluminum meat thermometers, the caustic in the bath will dissolve it, and the aluminum may ruin your

No thermometer?

Once the bath has settled down from the initial reaction, bring it up to heat until it's trying to simmer.
If you get it to where it bubbles around the parts, but not all over, it's at about 280. If it starts a low
boil all over, you're at about 300. That's OK. Above 310, and you're in danger of ruining your bath. The
chemicals will break down at 330 and become useless.

A Atheist will never be able to say, "I told you so!!"

Engine movies can be seen at: pileofiron

Last edited by Fred Van Hook; 12-23-2009 at 06:42:39 AM. Reason: sp
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Old 12-30-2009, 12:47:50 AM
Clark Bigger Clark Bigger is offline
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Default Re: How to blacken steel [no paint]

easist route {and cleanest} would be to take your parts to a gun shop...make sure all the red oxide [rust] is gone or that area will turn rust instead of black. I used an old formula wher I mixed all the chemicals for 15 years [4 tank system] we have a larger system [5 tank] and we use a comericial mix called black magic. the larger system is for high volume. if anybody wants my fomula or has questions send me a pm
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Old 01-06-2010, 02:01:09 AM
Big Diesel Big Diesel is offline
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Default Re: How to blacken steel [no paint]

Well just dont cover your head and the oil bucket with a towel and stay under there with the fumes and I personally think you'll be fine... I have been blacksmithing for about 15 years and use oil to quench and harden some steel and I'm still ok. I do use bee's wax on every thing I want to look good and stay pretty and black and not rust. But .50 cents to $1.00 will get you a cake of bee's wax that will last a very long time. If you know a bee keeper they will more than likely give you a little piece to do that with. Gun blueing will rust right up when left in the elements, hot,cold,humidity,condensation... Just wax it and I think you'll be pleased.

Thanks, T.A.
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Old 01-06-2010, 01:41:02 PM
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Default Re: How to blacken steel [no paint]

Whats all the fuss about oil. quenching in oil simply cools in uniform and creates a harder shell YET leaves it still maluable and doesnt immidiatly freeze the metal (which water does) and makes it brittle. Oil, used oil, you'll be fine. Just dont stand directly over the stuff. I've seen black smiths create spring steel in this fashion. There is a ball of fire, but no big deal. If it were me chances are i'd probably blue the metal (using gun metal blue) instead becouse the carbon coat-oil leaves on the metal really doesnt last long and eventually flakes off.

You do know however when you get metal hot enough to change color that the properties also change. So i hope this isnt an important peice to an important part of some machine.

Just my own un-bias opinion.
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Old 01-06-2010, 03:56:53 PM
ronald lachniet ronald lachniet is offline
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Default Re: How to blacken steel [no paint]

Originally Posted by Beez View Post
hi guys just want to know how to blacken steel without using paint, thanks for your help Beez
We used to blacken traps by boiling in walnut husks. If I recall they came out a nice black color.
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