Understanding Boiling of Black Oxide

2008-06-19T14:46:00.001-04:00

The concepts of heating and boiling black oxide are not so bad when you think about what is going on in a tank. Water boils at 212 F at sea level. To get it to boil at a higher temp you can put salt into it. If you put the right amount of blackening salts into the water (6#/gal) it will boil at 285F.

Boiling is different than just heating something to a set temperature. There must be extra heat from steam, gas flame or electric to get to temperature of 285F temperature, and then cause the phase change from liquid water to steam in the tank and boil. Once at the boil if there is too much heat it can boil over. So, adjust the heat by turning down the flame for a constant steady rolling boil, if the tank is boiling too violently. If it is barely boiling you may need to turn the flame up slightly. If you would like more info on the heating and temperature control of a black oxide tank in your business, please contact info@hubbardhall.com

Architectural Brown to Green on Brass and Copper

2007-12-20T16:09:00.000-05:00

Using Mi-Tiques for Architectural Brown to Green Color or Patina

These directions are aimed at new reproductions attempting to mimic older objects and not for working on valuable antiques. For true antiques you should consult experts in antique restoration and conservation techniques.

To give more realistic coloration for a green patina follow the natural progression of the material as it tarnishes. First the Copper, brass or bronze starts as a bright metallic gold or pink then it ages to a tan with time a deep brown color. This brown coloration can last a long time, but eventually will start to turn green reacting with atmospheric impurities such as sulfur compounds. So, to mimic this process requires several steps.

If you are doing this outdoors on an architectural reproduction then you need to protect the building and ground from contamination from the chemicals. Masking the area off with plastic drop cloth. All chemicals and rinses should be collected for proper disposal. Chemicals will stain concrete and stucco. Wear gloves and eye protection.

Product	Dilution	Temp	Time	Color
Mi-Tique 1791	15%	70 F / 25 C	1 min	Dark Brown
Mi-Tique 1792	25%	70 F / 25 C	2 min	Brown
Mi-Tique 1793	15%	70 F / 25 C	2 min	Black
Mi-Tique Green T2	35%	70 F / 25 C	Dry On	Blue Green
Mi-Tique Patina	100%	70 F / 25 C	Dry On	Yellow Green

Thoroughly clean the copper or brass. The metal has oils to help form it during manufacturing. Usually it also has an inhibitor on the surface to protect from tarnish. Aquaease SL 80 or Aquaease PL 72 A 32 are good cleaners.

Rinse off the cleaner with water. Collect the rinse water

Activate the brass or copper with an acid. Mi-Clean 24 is a weak acid cleaner which can clean and activate in one step. Acid salts such as Acid Salt M work as well. Although sulfuric acid 3% works it is very dangerous to handle, and dilution of sulfuric by adding water is dangerous. Always add acid to water.

Rinse again

Apply a brown or black base color: Mi-Tique 1791, 1792 or 1793 at 15 to 25 % work well as base colors. These can be dipped or applied with sponge or rags. Wear gloves and eye protection. Work quickly color will develop from 30 seconds to 1 min. Collect the run off these chemicals contain selenium and copper.

Rinse and collect this rinse water.

Stopping at Brown to Black color: If just the brown to black color is desired then wet or dry wipe off the smut or dusty layer and leave the brown. Use steel wool, or abrasive pads to relieve the pieces. Relieving or abrading back to metallic highlights gives an appearance of being handled where high areas are worn off. If the black brown is the final color then it can be protected by coating with wax, lacquer or oil at this point as top coat for the final color.

Continuing to Green: Pump spray, swab or brush on a 40% solution of Mi-Tique Green T2 over the brown/black colored surface. Allow the material to dry on and the green to blue green color to develop. Sometimes a quick spray or dip of hot water will give better color development. Mitique Patina is used at 100% as a spray to give a more yellow green color than the MT Green T2.

Allow to air dry. The green will form a powdery coating with poor adhesion.

Spray on an acrylic clean lacquer. Just a light spray to hold the green in place.

Antiquing, Blackening for Metals

Understanding Boiling of Black Oxide

Architectural Brown to Green on Brass and Copper