What type of glass should I use? – Chaos Help Center

There are certain glass rendering modes in the Refraction and the General section of the Physical and Legacy Corona Material. They should be used for setting up glass in different scenarios:

Physical Material:

''Thin shell (no inside)'' checkbox enabled - such material does not refract light and does not generate refractive caustics, which makes it render very fast. This mode should be used for very thin objects such as glass panes in windows, soap bubbles, light bulbs.
"Thin shell (no inside)" checkbox disabled - such material generates refraction and should be used for solid objects such as vases, glass furniture, glass objects with absorption color, liquids. You can toggle refractive caustics for this mode, however, enabling caustics will always make rendering much slower.

Legacy:

"Thin (no refraction)" checkbox enabled - such material does not refract light and does not generate refractive caustics, which makes it render very fast. This mode should be used for very thin objects such as glass panes in windows, soap bubbles, light bulbs.
"Thin (no refraction)" checkbox disabled - such material generates refraction and should be used for solid objects such as vases, glass furniture, glass objects with absorption color, liquids. You can toggle refractive caustics for this mode, however, enabling caustics will always make rendering much slower.