Over the last 15 years I have become the Pyrex bowl maven!  I thought I'd share what I learned!

WARNING; NEVER,EVER EVER WASH YOUR PRIMARY COLORED BOWLS IN THE DISHWASHER!! IT MAKES THE COLOR FADE.  IF YOU CONTINUALLY DO THAT THE COLOR WILL DEFINITELY LOSE ITS COLOR.

To age a bowl, you simply have to look at the thickness of the bowl. The thicker the bowl the older it is.  Bowls in a set that have the same thickness are the most valuable.

If  you are looking to buy a set be sure that they are all the same thickness (even the thinner bowls are valuable).  Check the bottom of the bowls, Pyrex used several different markings.  Again, if you want a set that is all of the same age and perhaps from the same original set, make sure the marking on the bottom are all the same.

Whenever you are checking for chips, hold the piece securely in one hand, close your eyes and run your fingers around the rim of the bowl. (You can do this with any glass, ceramic,  porcelain piece,etc.).Our fingers are more reliable than our eyes!  With the bowls, do this with the bottom as well. 

Pyrex came out with some bowls with patterns on them. I have only seen one:a large red one the size of the yellow bowl with gold leaves for Christmas.  (Even though it was not in great shape, I did buy it!)

There are bowls that came in other colors (gold, olive green, light orange) are most likely from the 1960's or 1970's. They are not worth as much as the primary colored ones.

If you are buying the bowls for resale, remember that those that went through the dishwasher are much less valuable than those that did not. 

 There are other Pyrex storage pieces that are lovely.  The same rule applies: no dishwasher! The rectangular pieces and the little rectangular pieces are most valuable if they have their glass tops.  Be sure to run your fingers around the clear glass tops to check for chips.  (If you ever come across a lone top, buy it!  The bowls are easier to find than the tops! ) You have a good chance of finding a bowl to go with it! There are sets of Pyrex usually with 4 pieces.  A true set is all the same color. 

Antique stores will sell the bowls anywhere from $40-65. Thrift shops may not have sets but they have plenty of singles! Grab them up!

The most exciting thing I have ever learned aout these bowls is that they are great to use for almost every meal, party or occasion!  They can go from the microwave right to the table!

I hope this helps and if anyone finds my info incorrect please let me know!