Conservation and Care of Glass Objects by Stephen Koob, Conservator for the Corning Museum of Glass, Archetype Publications Ltd., 2006, ISBN 1-904982-08-5, available for purchase at www.cmog.org

Dirt, deposits and sickness are each different problems, each with unique solutions.

Dirt and grease are most easily cleaned off with a simple solution of soap and water.

Deposits & Staining occur when dirt becomes bonded to the surface of the glass (glass is porous), commonly caused by minerals like calcium in regular tap water. This often requires chemical or mechanical methods for removal.

Sick or Crizzled glass is in a state of decay, though initially on a microscopic level. It is a result of compositional and environmental factors wherein the alkali in the glass is drawn out, undermining the structure of the glass.

Glass is easily damaged and, aside from gravity, water is the primary culprit, either through ambient humidity or direct contact. If you use your Blenko for liquids you must clean it out thoroughly after use. We do not recommend using decanters due to susceptibility to staining/sickness, nor do we recommend using pitchers due to the propensity for handles to crack.

When using vases for flowers, change the water often (about every 2 days) and do not use anything other than regular water; no flower preservative powders etc. Do not sit vintage glass in direct sunlight when filled with liquids; this can "bake in" dirt. Do not let the water go sour or scummy.

Do not subject your glass to varying temperatures or temperature extremes (example: sitting on a windowsill above a heater).

CAUTION: Whenever cleaning with water, please ensure that the water is the same temperature as the glass (room temperature) to prevent cracking from temperature differences. We recommend cleaning in a plastic sink or bucket rather than in a metal sink or tub to reduce the risk of damage. Also note that glass objects are more susceptible to breakage when they are full of liquid.

1. Soak in room temperature soapy water for no more than an hour.

2. Scrub lightly with a bottle brush, sponge or nylon cleaning pad. Do not use anything more abrasive. Forceful scrubbing can scratch the glass.

3. If you can not reach areas with a brush then add a few inches of soapy water and fill with a cup or so of rice grains. Swish this mixture around vigorously in a way that the rice rubs against the areas that need cleaning.

4. Rinse thoroughly and let drain until most of the water is gone, no more than 15 minutes should be necessary.

5. For decanters or items with small openings only: Pour in just enough rubbing alcohol (90% pure or higher) to swish around until it has covered all surfaces then let drain for 15 minutes but do NOT rinse.

6. Leave upright to dry in a dry, well ventilated area out of direct sunlight.

7. Do NOT put stoppers back on decanters until at least 24 hours has passed, if the weather is humid wait until you are certain absolutely all liquid has evaporated; trapped humidity can cause staining/sickness.

Iron stains are usually soluble with 5-10% oxalic acid in water. They may require rubbing with a Q-tip, cloth or sponge. When done rinse with water.

For carbonate deposits from evaporated tap water use 3-5% nitric acid & water on a cotton swab, immersion may be necessary. Deposits should soften or dissolve within 2 minutes. Then clean with soap & water as above.

Denture cleaner pills or liquid are NOT appropriate for cleaning Blenko, it risks causing further staining

Soaking in vinegar (a mild acid) is thought by some to be beneficial for removing certain types of deposits, however, it will not undo Sickness. More importantly, in our experience vinegar can make staining more pronounced - we do NOT recommend it.

We do not recommend the use of any household cleaners on Blenko glass; they are all liable to cause damage.

We do not recommend the use of caustic acids other than the two (oxalic & nitric) mentioned above.

Sick glass as well as most stains can only be cleaned by polishing / tumbling.

A word on using restorers: most glass restorers in the US are self-taught hobbyists and not formally trained. We recommend asking them about their professional experience and credentials.

Virtually all restorers do work "at your risk" meaning that once you have handed the item over to them to perform the requested work, they will not be liable for any damage that may result. This risk is a necessity as it is not possible to insure glass or other extremely fragile items while elective work is being done on them. If the item should break or be otherwise damaged the restorer is not bound to cover your cost for the item and most household or other insurance policies will not cover the loss. Reputable restorers will have a policy of not billing a client for work when an item is further damaged by them. Ask about such a policy in advance.

Inspect all glass closely before giving it to a restorer, note any pre-existing defects or condition / execution issues. Chords or large bubbles indicate weaknesses and make the glass susceptible to breakage in cleaning.

Be sure to tell your restorer that Blenko is particularly "soft" (porous) soda-lime glass.

When working on rims, many restorers will want to finish the rim in the "best" (standard) way; that is with a bevel, which does not chip as easily. Bevels are inappropriate for almost all Blenko. You must specify that you want to maintain the existing "fire-polished" rim look.

For bowls, plates or exterior surface stains most glass restorers can polish these off with conventional polishing methods.

For internal stains or sickness on vessels, "tumbling" will be necessary.

Tumbling involves filling the item with an abrasive material (such as lead filings, bb pellets, felt, etc). The top of the item is then sealed and it is inserted horizontally into a tube and secured in place. The tube, lying horizontally is then rotated on a machine for an extended period (varying from hours to weeks). The duration depends on both the degree of staining and the type of glass.

WARNING: tumbling is not a problem-free process. A not uncommon by-product of tumbling is variously known as "rippling" or "the orange peel effect" wherein the inside of the bottle will develop a disfiguring texture (like rippled water or the surface of an orange). The risk of this is generally greater than many assume. Be sure to ask any tumbler in advance about this problem and what their payment policy is if rippling should occur.