wow thanks Larry! that's a boatload of good info right there. next time i'll try and use gravity/surface tension (hot glass wants to ball up it seems?) to round it out until the very final finishing.
and i'll report back. thanks again LarryC
Quote:
Originally Posted by LarryC
yes. It is due to the difference in viscosity between the colored and most likely stiffer backing and the softer clear lens as others have already suggested. My standard designs are 2.25" or so and I used to get this on larger marbles that needed lots of trips into my mold. The glass is being overworked and the damage, permanent devit, is showing up where its worst at that interface. It gets progessively worse so it is not surprising that it shows up at the end. I fixed it completely by reducing the amount of mold time to a minimum. When this was happening I was using the mold throughout the three hours or so it takes me for most of my marbles. Now I only use the mold for the final shaping. I keep them mostly round throughout with just heat and gravity. This is really pretty common. Why is it worse as the marbles get bigger? Not sure, but in my experience, everything gets harder and more critical as the mass grows. Also, be sure you clean your molds regularly. I use denatured alcohol to clean mine every day. You may be amazed by how much this will increase the clarity and luster of your lenses.
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