Use a glass with the thickness specified in the forms or construction with smooth surface. Regular non-transparent bubbles or not as there are no waves or crack and abrasion and smearing.
Use clear glass with a thickness as specified in the form or construction of a smooth surface. Not always clear bubble or not is not a crack or a scratch fouling.
Make use of the glass with a thickness as specified in the form or construction items have a smooth surface. Consistently clear no bubbles or wave is broken or scratched stained.