Champlevé & Etching Tutorials » Discussions

Acid Etchants for METALS

• Trish White

  

  Leader
   

  May 11, 2010

  METAL - Usually 14 or 16 gauge metal is used to etch a piece for enameling, especially a large piece because the heavier metal will have structural strength, even after it is etched.

  Etch at least halfway through the metal if you want to have plenty of room to inlay color, but not always necessary. On Large vessel forms use 14 or 16 gauge metal, but on smaller jewelry pieces, especially if they are formed, 18-20 gauge metal works well, depending on the function of the piece.

  
  

  ACIDS - Though Nitric Acid can also be used to etch silver and copper, Ferric Nitrate and Ferric Chloride are safer, and more available and bite the metal more cleanly and can be used with a wider variety of resists. NItric is more hazardous to work with, doesn't bite the metal as cleanly and there are fewer resists that can be used with nitric acid because it is so volatile, bubbling and lifting resists during the etching process. The disadvantage of the ferric acids it that they etch so slowly, but it is worth the extra time it takes to etch because the slow bite not only gives a cleaner etch with less ragged edges it also makes it possible to use more resists. With these ferric based acids you an use many resists for shallow etches (such as crayon, permanent marker, glue etc) . My favorite resist is an oil based pen or marker over circuit board heat transfer paper (also called PNP paper)

  
  

  FERRIC CHLORIDE - is inexpensive and readily available from Chemical Supply houses on line and can be used straight from the bottle. It also comes in crystal form and can

  be mixed (13 oz. of ferric chloride etching crystals to 16 oz. of water). Ferric Chloride will etch copper, but NOT silver. A mustard colored residue is left on the surface of copper when etching with ferric chloride and it should always be neutralized and scrubbed off the metal with ammonia and water after etching. 

  
  

  ACID STORAGE AND DISPOSAL:

  
  

  Storing Ferric Chloride and Ferric NItrate in opaque containers helps to preserve their shelf life and usually when they come from the Chemical Company they are in these type of containers. You can reuse the acids, but the longer the acid is used and the more pieces it etches, the weaker it will become and etching will be slower. If you do reuse the acid, mark the date mixed, amount of usage and how long. Ferric Nitrate seems to weaken more quickly than Ferric Chloride. Etching slowly is actually preferable for some purposes, as the slower the acid etches, the more cleanly it bites with less undercut. Neutralize all acids  before preparing it to go the Hazardous Waste Authorities and mark the containers with the name of the Acid and that it has been neutralized. Do NOT put any acids down the sink. Though these chemicals may not be hazardous to the environment before they are used, through the etching process they will become a combination of the original chemical with copper chloride (ferric chloride) and silver nitrate (ferric nitrate) in solution The ferric ions are not particularly hazardous to the environment, but what is left in the solution after etching IS.

  
  

  FERRIC NITRATE - is the acid used for etching on silver. It etches very clean and also works well with an oil based paint and heat transfer paper (PNP). It will also etch copper, but Ferric Chloride is much less expensive and seems to last longer.

  500 grams of Ferric Nitrate crystals are mixed with 1 pint of hot water until they dissolve (or 3136 grams to a gallon of water if you use a spray etching machine).

  Ferric Nitrate is basically NITRIC ACID, which contains iron and it is neutralized with baking soda.

  
  

  Disposal -  To make Ferric Chloride safe for disposal, you must add SODIUM CARBONATE

  (washing soda) or SODIUM HYDROXIDE to neutralize it until the ph value goes up to 7.0 and 8.0 (must be tested with indicator paper). Copper will be left in the solution as a sludge. Allow the sludge to settle pour off the liquid and further dilute it with water .The sludge should be collected in plastic bags or containers and disposed of as required by local waste authorities.

  
  

  To remove the silver dissolved in the Ferric Nitrate solution, add SODIUM CHLORIDE solution to the mix (baking soda). The silver will precipitate out as a white solid, silver chloride and the resulting solution could be diluted and disposed of without concern.

  But most often, even when using Ferric Nitrate, you are etching sterling which contains copper, or perhaps you have just used copper. This means that copper ions are dissolved in the solution and again, copper ions ARE hazardous to the environment and can be removed as explained when using Ferric Chloride, but should NOT be put down the drain or into the environment.

  
  

  PRECAUTIONS;

  
  

   1. Always wear rubber gloves, aprons and eye protection when using ACIDS.

  
  

   2. Do Not breathe fumes - WEAR a mask and work in a well ventilated area or under a     fume hood.

  
  

   3. Depending on the ACID used, keep baking soda and ammonia close by for neutralizing spills.

  
  

  4. Always keep ACIDS covered when not in use.

  
  

  5. When mixing ACID, add ACID to water( to reduce the chance of splashing the acid on yourself).

  
  

  6. Label all stored ACID with the solution and date. Keep notes of how often the ACID has been used to determine its strength for estimating etching times.

  
  

   7. Clean and neutralize metal pieces after removing them from ACID.

  
  

  (notes from Linda Darty - Acid Etching Workshop)

  METAL - Usually 14 or 16 gauge metal is used to etch a piece for enameling, especially a large piece because the heavier metal will have structural strength, even after it is etched.

  Etch at least halfway through the metal if you want to have plenty of room to inlay color, but not always necessary. On Large vessel forms use 14 or 16 gauge metal, but on smaller jewelry pieces, especially if they are formed, 18-20 gauge metal works well, depending on the function of the piece.

  
  

  ACIDS - Though Nitric Acid can also be used to etch silver and copper, Ferric Nitrate and Ferric Chloride are safer, and more available and bite the metal more cleanly and can be used with a wider variety of resists. NItric is more hazardous to work with, doesn't bite the metal as cleanly and there are fewer resists that can be used with nitric acid because it is so volatile, bubbling and lifting resists during the etching process. The disadvantage of the ferric acids it that they etch so slowly, but it is worth the extra time it takes to etch because the slow bite not only gives a cleaner etch with less ragged edges it also makes it possible to use more resists. With these ferric based acids you an use many resists for shallow etches (such as crayon, permanent marker, glue etc) . My favorite resist is an oil based pen or marker over circuit board heat transfer paper (also called PNP paper)

  
  

  FERRIC CHLORIDE - is inexpensive and readily available from Chemical Supply houses on line and can be used straight from the bottle. It also comes in crystal form and can

  be mixed (13 oz. of ferric chloride etching crystals to 16 oz. of water). Ferric Chloride will etch copper, but NOT silver. A mustard colored residue is left on the surface of copper when etching with ferric chloride and it should always be neutralized and scrubbed off the metal with ammonia and water after etching. 

  
  

  ACID STORAGE AND DISPOSAL:

  
  

  Storing Ferric Chloride and Ferric NItrate in opaque containers helps to preserve their shelf life and usually when they come from the Chemical Company they are in these type of containers. You can reuse the acids, but the longer the acid is used and the more pieces it etches, the weaker it will become and etching will be slower. If you do reuse the acid, mark the date mixed, amount of usage and how long. Ferric Nitrate seems to weaken more quickly than Ferric Chloride. Etching slowly is actually preferable for some purposes, as the slower the acid etches, the more cleanly it bites with less undercut. Neutralize all acids  before preparing it to go the Hazardous Waste Authorities and mark the containers with the name of the Acid and that it has been neutralized. Do NOT put any acids down the sink. Though these chemicals may not be hazardous to the environment before they are used, through the etching process they will become a combination of the original chemical with copper chloride (ferric chloride) and silver nitrate (ferric nitrate) in solution The ferric ions are not particularly hazardous to the environment, but what is left in the solution after etching IS.

  
  

  FERRIC NITRATE - is the acid used for etching on silver. It etches very clean and also works well with an oil based paint and heat transfer paper (PNP). It will also etch copper, but Ferric Chloride is much less expensive and seems to last longer.

  500 grams of Ferric Nitrate crystals are mixed with 1 pint of hot water until they dissolve (or 3136 grams to a gallon of water if you use a spray etching machine).

  Ferric Nitrate is basically NITRIC ACID, which contains iron and it is neutralized with baking soda.

  
  

  Disposal -  To make Ferric Chloride safe for disposal, you must add SODIUM CARBONATE

  (washing soda) or SODIUM HYDROXIDE to neutralize it until the ph value goes up to 7.0 and 8.0 (must be tested with indicator paper). Copper will be left in the solution as a sludge. Allow the sludge to settle pour off the liquid and further dilute it with water .The sludge should be collected in plastic bags or containers and disposed of as required by local waste authorities.

  
  

  To remove the silver dissolved in the Ferric Nitrate solution, add SODIUM CHLORIDE solution to the mix (baking soda). The silver will precipitate out as a white solid, silver chloride and the resulting solution could be diluted and disposed of without concern.

  But most often, even when using Ferric Nitrate, you are etching sterling which contains copper, or perhaps you have just used copper. This means that copper ions are dissolved in the solution and again, copper ions ARE hazardous to the environment and can be removed as explained when using Ferric Chloride, but should NOT be put down the drain or into the environment.

  
  

  PRECAUTIONS;

  
  

   1. Always wear rubber gloves, aprons and eye protection when using ACIDS.

  
  

   2. Do Not breathe fumes - WEAR a mask and work in a well ventilated area or under a     fume hood.

  
  

   3. Depending on the ACID used, keep baking soda and ammonia close by for neutralizing spills.

  
  

  4. Always keep ACIDS covered when not in use.

  
  

  5. When mixing ACID, add ACID to water( to reduce the chance of splashing the acid on yourself).

  
  

  6. Label all stored ACID with the solution and date. Keep notes of how often the ACID has been used to determine its strength for estimating etching times.

  
  

   7. Clean and neutralize metal pieces after removing them from ACID.

  
  

  (notes from Linda Darty - Acid Etching Workshop)
• M. Quinnan Whittle

  

  Member
   

  August 24, 2011

  For a solution that will work faster, etch cleaner, and eliminate the sludge on the bottom of your etching container, try combining ferric chloride and citric acid.  This is referred to as the Edinburgh Etch Solution, named after the chemistry department at the U of Edinburgh where it originated.  To make citric acid solution, add 1-1/2 cups distilled water to 1/2 cup citric acid powder (technical grade is cheaper than food quality) available online or (food grade) at your grocery store.  This makes more than you need for the following recipe, so store the excess mixture in a plastic container.   Edinburgh Etch Recipe:   Pour 4 ounces of the liquid citric acid solution into a plastic or glass container with a non-metalic lid and slowly add 16 ounces of ferric chloride solution and mix with a plastic or wood stir stick. (It is basically a ratio of 1/5 citric acid solution to 4/5 ferric chloride) Drop in a small piece of copper to take the bite off.  A short fingernail size snippet of copper should do it.   With this solution it is no longer necessary to etch your metal upside down.  I use a tall and narrow plastic container and place the copper on a longish piece of duct tape or packing tape that I clip to the outside of the container.  The tape works nicely to protect the back of the metal, suspend it in the solution, and to lift the piece out after etching. You might also write the time you put the piece in the etchant on the tape as a reminder.  In class, I have the students put their initials on the tape too.  Use all the recommended safety precautions listed above.

   

  I would caution against mixing your own ferric chloride solution from crystals.  The mixing process is very hazardous, and why risk it when saturated solutions are readily available.  Stores that cater to the printed circuit board hobbyists are good sources for ferric chloride--which is generally marketed at PCB etchant. The fumes of the solution are not considered hazardous to humans (at least not when etching copper) but they are corrosive to metals, so keep a tight lid on your solution, especially if it is stored anywhere near your pipes.  A bottle of this solution will last for a year or even two in most studios.  

   

   

  For a solution that will work faster, etch cleaner, and eliminate the sludge on the bottom of your etching container, try combining ferric chloride and citric acid.  This is referred to as the Edinburgh Etch Solution, named after the chemistry department at the U of Edinburgh where it originated.  To make citric acid solution, add 1-1/2 cups distilled water to 1/2 cup citric acid powder (technical grade is cheaper than food quality) available online or (food grade) at your grocery store.  This makes more than you need for the following recipe, so store the excess mixture in a plastic container.   Edinburgh Etch Recipe:   Pour 4 ounces of the liquid citric acid solution into a plastic or glass container with a non-metalic lid and slowly add 16 ounces of ferric chloride solution and mix with a plastic or wood stir stick. (It is basically a ratio of 1/5 citric acid solution to 4/5 ferric chloride) Drop in a small piece of copper to take the bite off.  A short fingernail size snippet of copper should do it.   With this solution it is no longer necessary to etch your metal upside down.  I use a tall and narrow plastic container and place the copper on a longish piece of duct tape or packing tape that I clip to the outside of the container.  The tape works nicely to protect the back of the metal, suspend it in the solution, and to lift the piece out after etching. You might also write the time you put the piece in the etchant on the tape as a reminder.  In class, I have the students put their initials on the tape too.  Use all the recommended safety precautions listed above.

   

  I would caution against mixing your own ferric chloride solution from crystals.  The mixing process is very hazardous, and why risk it when saturated solutions are readily available.  Stores that cater to the printed circuit board hobbyists are good sources for ferric chloride--which is generally marketed at PCB etchant. The fumes of the solution are not considered hazardous to humans (at least not when etching copper) but they are corrosive to metals, so keep a tight lid on your solution, especially if it is stored anywhere near your pipes.  A bottle of this solution will last for a year or even two in most studios.