LETTER TO THE EDITOR

1.1 To the Editor:

In a technical note published in the last issue of the Journal (25 [1986]: 93–96), I referred to the use of glass microballoons for peening or air abrasive use. Phoebe Dent Weil has kindly alerted me to the fact that although the terms microsphere and microballoon are often used interchangeably, the distinction between them is extremely important.

Both the solid microspheres and hollow microballoons may be used in fill materials, but it is the solid microspheres alone which are suitable for glass peening techniques. I thank Phoebe for suggesting that this distinction be clarified.