Prep the Copper
- Cut the copper – this is best on copper at least .015″ thick
- if you are planning on having it water jet cut later, add at least 1.5″ to your sizes
- Sand the front with a 3M coarse grinder pads. This will hide the scratches that copper inevitably gets and create a nice pattern in the metal.
- Alternately, use an orbital sander, 50 grit. This is an attractive pattern.
- If you are planning on brazing decorative lines – e.g. ovals, circles, zig zags – on the copper, now is the time to do that
- Typically, this copper red patina is done near the garage door opening with the garage door open for ventilation
- also to facilitate taking the copper outside to wash with the hose afterwards
- also, we want the salt to be as near the door as possible. Salt tends to absorb water from the air and it is hard on the concrete when it gets ground into it. Sweep it us or out as soon as possible.
- Set up some concrete blocks on a table or sawhorses with bricks on top of the concrete blocks
- You want the copper sheet to be just above the height of your elbows.
- make sure there is room enough below the copper to use the rosebud tip – 4-6″ is good – that’s one purpose of the bricks
- place the copper on the bricks – you are ready to start
Copper Red Patina – Technique
- Lightly sprinkle regular table salt on the copper – use a big salt shaker – you will eventually use a lot of salt and it is easier to not stop and refill it.
- Alternately, sprinkle on the copper a 5:1 blend of salt:baking soda – this gives very rich reds, some bright reds, purply reds and dark reds with some blacks and very little of the oranges and browns. Also, doesn’t mottle like salt does.
- Baking soda also seems to help the copper red patina stick to the copper better
- Put the rosebud tip on the oxy-acetylene torch
- Turn up the pressure on the oxygen and acetylene regulators. Both regulators should be set in the 5-10 range – adjust as needed.
- Turn on the acetylene only, light the torch and, as quickly as possible, get the oxygen dialed in to help minimize soot in the workplace. Those little black flakes will float around and stick to everything.
- You don’t want an excess of oxygen – this tends to blow a hole in the copper. An excess of oxygen is a flat flame with no inner orange cone.
- You want an inner orange cone about 1-2 inches long.
- The torch will be quite loud. If it isn’t roaring, turn it up. You will need the heat.
- Remember – if the copper is taking too long to heat, put the torch closer to the copper and/or increase the flow at the regulators. If you are burning holes, turn down the heat or back away from the copper.
- Use your heaviest, thickest welding gloves, the ones that go half-way up your arms and look like oven mitts.
- The torch goes under the copper – You heat the copper from below until it gets red hot to get the copper red patina
- if salt is already on the copper you don’t have to sprinkle more, or you can – it’s up to you
- generally I am sprinkling salt at least 50% of the time I am torching
- if the copper is red hot and you sprinkle a little salt on it you will get a lovely mottled effect spots of orange amidst the red
- Concentrate carefully and keep the torch moving. It is very easy to make big holes in the copper with this technique. Don’t try to talk to anyone while you are doing this. Focus.
- Start the copper red patina with the corners because corners are easiest to heat – also easiest to melt! In general, you want to do ‘U’ or ‘ZigZag’ patterns with the torch but other patterns are interesting too
Copper Red Patina – Details
- A black crust will form which will turn red as it cools
- As you move to the next area, be careful not to go over the area you just did
- If you do go back over a previously torched/salt-melted area, the crust on the copper red patina will peel off and leave an orange and black patina – sometimes this is desirable for variation.
- If you sprinkle the salt on before the torching, you will have a smooth copper red patina
- If you sprinkle the salt on during the flaming, you will have a mottled pattern with lighter specks where the salt fell on the red-hot metal.
- If you don’t put any salt on at all, the copper will go orange if you just heat it slightly, brown if heated almost red, black if it went to full cherry red
- Slowly and methodically torch the whole piece. Don’t jump around – It is easiest to heat the metal next to where it has already been heated
- If there is brass melted on the copper, avoid melting the brass any further. Usually people like texture in the brass.
- Also – avoid heating the areas near the brass that are golden and champagne and copper colored – these are beautiful just as they are – don’t lose more than 50% of these colors.
- Note that the bricks will get in your way and you will have to move them one by one as you go around the piece.
- Plain salt creates a mottled, organic-looking mixture of bright reds, dark reds, oranges, browns, blacks and salmons (near a flux bronzed line). You do not want to just get reds.
- Your goal is to get the copper just hot enough to melt the salt – that’s it. This is a dull reddish color. If you go to a bright reddish color, that’s too hot! You won’t get a nice variegated patina.
- If you go back over an area on which you’ve already melted the salt, you will get nice speckled oranges.
- If you go near an area and get it hot but don’t melt the salt, you will get nice blacks and browns.
- You want this variation in color – not all one solid color
Copper Red Patina – Rinse & Dry
- When you have finished, wait 2 minutes for the copper to cool a bit.
- Turn off the torch and take the copper over to the washing area.
- Put it upside down on something non-scratchy – wood, silicone paper or grass. Not foam – it might melt. The copper red patina is soft at this point. Try to avoid fingerprints, etc.
- Rinse and cool the back briefly.
- Then flip over the patinated copper.
- You have about 1 minute to get it rinsed off. Rinse quickly with a soft stream ( too much water at this point can wash off some of the delicate new patina).
- Don’t try and get all the salt and baking soda off just yet.
- The copper red patina is very fragile when new and wet and can run down the surface in streaks. It needs to dry to really lock on to the copper.
- To dry – Hold it by the edges for 20 seconds to let the water drain off, then set it down flat on the floor in front of a fan to dry
- Do not let it dry lying in the sun – it seems to be light- and/or heat- sensitive when new and will turn brown
- don’t dry leaning against the wall – you will get lots of streaks
Copper Red Patina – Repairing a patina
- If you’ve blown some holes in the copper, normally those will have to be repaired by brazing on a small patch from the backside – fix those first
- holes can also be fixed afterwards with epoxy and paint
- If you’ve done an unsatisfactory patina, there are a couple of ways to fix it.
- First, let the copper red patina fully dry
- Then cover half the patina with a wet towel and try to redo the technique on the uncovered area. If that works, redo the process with the wet towel over the other half.
- If that doesn’t work, you will have to strip off the patina – 3M pad on your grinder or chemically with dilute nitric acid plus oxalic acid plus glacial acetic acid
- If you have brazed on a bronze decorative line, protect it with either Cool Blue, Handi Jig or a Baking Soda/Clay mixture
Copper Red Patina – Remove the Rest of the Salt
- After the patinated copper has dried, you will need to lay the metal flat (face up) on the floor or table and cover the surface with wet towels.
- The towels should be on for at least 12 hours. The purpose is to hydrate, soften and remove all water-soluble flux, baking soda, salt, etc. from the copper red patina
- The next day, remove the towels and carefully clean off the surface with a light water mist.
- Inspect the surface for any remaining salt or white flecks. Try to gently rub or pry them off. You may have to redo the towel technique.
- If any green patina or staining is evident, rub that off with towel and water, then rinse again
- The patina will be soft and powdery until it is clear coated. Until then, protect it from scratches with silicone paper or foam.
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