Correspondance with lens design software maker

[Ole]

Yes, you should always heat it slowly at first to drive off excess water. Then you won't get hot liquid borax splattered all over.

We made borax glass tablets in university for X-ray spectroscopy - a little powdered rock and a lot more borax. Then stand well back while the automated smelter did its work.

[Mustafa Umut Sarac]

Thank you , Ole