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Hi. Paul Ysart paperweights from the 1930s, especially the rather tinted glass ones, seem prone to cracking. I don't think they were always annealed properly. It is always important to check the base of seemingly sound Ysart paperweights from this era, as quite a few have cracks radiating from the pontil mark. Repeated heating and cooling during the day/night cycle, or even getting water into the cracks can lead to these growing. (I think water can affect the surface energy needed for Griffith crack growth, but it is a complicated subject). I have heard of 3 people who have had Paul Ysart weights crack in two (or more) whilst the weights were just sitting in a display cabinet.
People have tried various ways to repair them...but I have yet to hear of anyone succeeding. I think that once they are cracked, that is the end of it. If they look good on display, great, but the market value is negligible.
Alan