How To Detect "re-worked" Marbles

Several Midwestern glass workers have been "reworking" antique and collectible marbles. The reworked pieces are suspected of having been created from original factory scraps and original damaged marbles. These bits and pieces are heated and joined in unusual styles and color combinations that would make them very desirable if old. According to Stanley Block of Block's Box, a leading appraiser and auctioneer of antique and collectible marbles, there are several ways to detect reworked marbles.

First, since these marbles are made of pieces from several different marbles, you can detect these differences with a black light. All glass of the same color in original marbles reacts the same to black light. If you have two spots of white glass, for instance, in the same marble and each spot of white fluoresces differently, it means that one of the spots is not original.

Secondly, look at the surface with a loupe. Reheating and reworking the marbles creates a rough surface. Grinding and polishing the surface opens air holes just beneath the surface. The edges of these areas--reduced by grinding--have sharp, abrupt edges. Similar irregularities in the surface of original marbles are smooth as a result of intense heat and melting at the time they were made.

Cross section of marble surface

Fig. 1 Reworked surface showing sharp edges in pits and holes ACRN caused by polishing the reworked surface

ACRN
illustration

Fig. 2 Edges of pits and holes in original surface are smooth because they are partially melted during original making