Iv had powdered n cleaned my crystal enamel shades...bt i did not get a chance to use dem..its been 3 to 4 weeks...they r transparent shades....so is it advisable to use them..

If you have only sifted them clean, then they are fine in the jar. But if you have been working with the enamels on a project and have some wet left over, then they should be kept in a jar under water until you are ready to re-use. This is what I was told by my instructors at various workshops. We will see what anyone else suggests. 

It should be OK.  Wash the powder well, and most likely they have not oxidized.  If you see lots of white stuff floating like dandruff, it might be oxidation, which is not good.  I keep my enamels wet for long periods of time (years), without any damage, but it may depend on the color and type.  If you are not sure, fire a pinch on some scrap, see if it fires right.

Lillian, this information is a tremendous help to me -- thank you! In all the books I've read no one actually mentioned the amount of time you could leave enamels wet. I don't wash a great deal at one time, but I sometimes want to use the colors for more than one project and can't get to the next 'studio day' for a week. I would always throw the washed enamels away and start again. It's good to know I could still use them if stored as you suggest.

Hi Aarti. My only teacher in Enamel late Mr. Chandrakant Mhartre used to keep his powdered enamel stock in glass jars dipped in ample water and store. His consumption was very high so he used to keep at least 2 kgs. of each shades ready. When I asked why you store enamels in water. His answer was and I think was very scientific, that because of water, enamels do not come in contact with air and thus do not get oxidized. And because they don't oxidized, transparents remains transparent. Opaques, no problem. Regards