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I have read a couple of posts lately that touch on this subject.
Ebay and the internet have made it easy to purchase original ceramic and glass artifacts from all over the world, and from various environments. Some are archaeological artifacts others from old collections and storage.
There are a few things to keep in mind if you are going to use or display them.
Here are a few non-scientific suggestions to use at home.
Cleaning;
Usually warm soapy water is enough. If it looks clean after you wash it well it usually is, especially glass and porcelain, stoneware to a degree and you really cannot be sure with earthenware. There are many exceptions. Always err on the side of caution, just because it looks clean does not mean you can actually use it for food or beverage storage.
Never use bleach. If you must, never at full strength. It’s bad… very bad. If you feel the need to use it because there is a mold or mildew problem, put about an ounce of regular bleach in a gallon of water and soak the artifact a couple of hours. Rinse well, wipe it off, let it dry and then rinse again. I don’t like bleach on anything. Never use bleach on fine porcelain or earthen ware. It is ok on glass and heavy glazed stoneware with no cracks.
I recommend powdered citric acid and a soft brush. Mix the citric acid as per the instructions. Rinse well in distilled water. Air dry. Citric acid is actually a crystalline powder and can be use on glass, and stoneware with a good deal of success.
It can be used on all nonporous ceramics and glass. It will clean almost anything from the artifact surface, including paint from old bottles and some 19th century transfer prints on stoneware. It acts as a buffer, eleminates trace metal ions, replaces phosphates, removes metal oxidation products from the surface of ferrous and non-ferrous metals eliminates chloride stress cracking and is rapidly biodegradable. It also decalcifies. Shell and coral encrustations don't stand a chance.
Citric Acid comes in food grade and a commercial cleaning grade with a mild soapy additive. Both work well as a cleanser but dont ingest the soapy stuff.
But be careful and take your time. It is easy to find on and offline.
A good way to judge if a cleaning is going to be harmful to a surface decoration is to carefully rub a damp q-tip on a small area. If the decoration changes color, light to dark and leaves a residue on the cotton then don’t clean or use it (if you want to preserve the decoration).
Look for cracks in ceramics. Any cleaner will get into the body of the ware and you will have a devil of a time getting it out.
One thing to keep in mind is not to apply a treatment to an artifact that cannot be removed, reversed or improved upon when something better comes along. Permanent treatments can sometimes cause more harm than good.
Contamination;
Some vessels coming from Western Europe are being looted from old public sewers and dumps. If the ceramics have a sour “sewer” smell then it has been leeched with salts from the waste and can never be used for anything but display. These salts will eventually destroy the vessel once it dries. Conservation can be very costly. Soaking it periodically in distilled water can slow this process but the effort is really not worth it without the proper additives to stabilize the artifact.
As stated in another post poisons are a real risk, especially in ceramic containers. Though most poisons were stored in glass and not pottery you can never know what the individual owners put in them before you. As non-porous as glazed stoneware appears it does have wicking properties and can harbor a poison with a long shelf life.
Many poison bottles have specific shapes, but again poison can be housed in anything.
Glazes can be an issue too. Lead, magnesium and cobalt were popular elemental tints for glaze. While magnesium in prescribed doses is beneficial it was often used along with lead. Be careful.
If you have a ceramic container that you actually use in a living History setting and have any doubts about it I’ll be glad to give you any feedback or refer you to someone who can.
__________________________________________________ _______________
I have touched on this subject very lightly. There are scores of effective treatments that can be used and many more precautions that can be addressed.
But that is for another time and another forum...
Ebay and the internet have made it easy to purchase original ceramic and glass artifacts from all over the world, and from various environments. Some are archaeological artifacts others from old collections and storage.
There are a few things to keep in mind if you are going to use or display them.
Here are a few non-scientific suggestions to use at home.
Cleaning;
Usually warm soapy water is enough. If it looks clean after you wash it well it usually is, especially glass and porcelain, stoneware to a degree and you really cannot be sure with earthenware. There are many exceptions. Always err on the side of caution, just because it looks clean does not mean you can actually use it for food or beverage storage.
Never use bleach. If you must, never at full strength. It’s bad… very bad. If you feel the need to use it because there is a mold or mildew problem, put about an ounce of regular bleach in a gallon of water and soak the artifact a couple of hours. Rinse well, wipe it off, let it dry and then rinse again. I don’t like bleach on anything. Never use bleach on fine porcelain or earthen ware. It is ok on glass and heavy glazed stoneware with no cracks.
I recommend powdered citric acid and a soft brush. Mix the citric acid as per the instructions. Rinse well in distilled water. Air dry. Citric acid is actually a crystalline powder and can be use on glass, and stoneware with a good deal of success.
It can be used on all nonporous ceramics and glass. It will clean almost anything from the artifact surface, including paint from old bottles and some 19th century transfer prints on stoneware. It acts as a buffer, eleminates trace metal ions, replaces phosphates, removes metal oxidation products from the surface of ferrous and non-ferrous metals eliminates chloride stress cracking and is rapidly biodegradable. It also decalcifies. Shell and coral encrustations don't stand a chance.
Citric Acid comes in food grade and a commercial cleaning grade with a mild soapy additive. Both work well as a cleanser but dont ingest the soapy stuff.
But be careful and take your time. It is easy to find on and offline.
A good way to judge if a cleaning is going to be harmful to a surface decoration is to carefully rub a damp q-tip on a small area. If the decoration changes color, light to dark and leaves a residue on the cotton then don’t clean or use it (if you want to preserve the decoration).
Look for cracks in ceramics. Any cleaner will get into the body of the ware and you will have a devil of a time getting it out.
One thing to keep in mind is not to apply a treatment to an artifact that cannot be removed, reversed or improved upon when something better comes along. Permanent treatments can sometimes cause more harm than good.
Contamination;
Some vessels coming from Western Europe are being looted from old public sewers and dumps. If the ceramics have a sour “sewer” smell then it has been leeched with salts from the waste and can never be used for anything but display. These salts will eventually destroy the vessel once it dries. Conservation can be very costly. Soaking it periodically in distilled water can slow this process but the effort is really not worth it without the proper additives to stabilize the artifact.
As stated in another post poisons are a real risk, especially in ceramic containers. Though most poisons were stored in glass and not pottery you can never know what the individual owners put in them before you. As non-porous as glazed stoneware appears it does have wicking properties and can harbor a poison with a long shelf life.
Many poison bottles have specific shapes, but again poison can be housed in anything.
Glazes can be an issue too. Lead, magnesium and cobalt were popular elemental tints for glaze. While magnesium in prescribed doses is beneficial it was often used along with lead. Be careful.
If you have a ceramic container that you actually use in a living History setting and have any doubts about it I’ll be glad to give you any feedback or refer you to someone who can.
__________________________________________________ _______________
I have touched on this subject very lightly. There are scores of effective treatments that can be used and many more precautions that can be addressed.
But that is for another time and another forum...