Choosing glass for light

• Cathedral is transparent and colored. Light passes through it and it glows. It also shows you whatever is behind it, which is wonderful over a garden and unfortunate over a neighbor's drainpipe.
• Opalescent is dense and milky. Light lands on it rather than passing through, so it reads as color in any light, which is why lampshades and anything backed by a wall use it.
• Wispy, streaky and ring-mottled sit between the two: opal swirled through cathedral. They carry movement, and they are the ones that punish you for ignoring grain direction.

A useful shorthand: cathedral is for looking through, opalescent is for looking at. Most panels want both, and the contrast between them is doing more work than the colors are.

1. 1Hold it up, do not lay it downAgainst a window for a window panel. Against a lamp for a lampshade. On a white bench for anything that will hang against a wall. Three completely different answers from one sheet.
2. 2Step back six feetTexture and streak that read beautifully at arm's length often disappear at viewing distance, and a sheet you rejected as “too busy” is frequently perfect from across the room.
3. 3Check it at nightA window panel spends half its life unlit. Dense reds, deep ambers and heavy opals all go to near-black with no light behind them. If the design has to read at night, it needs light values in it somewhere.

The commonest mistake in glass selection is picking colors that differ in hue but not in value: a mid green beside a mid blue beside a mid teal. They are three different colors and the panel still reads as one flat shape, because the eye separates shapes by lightness long before it separates them by hue.

Most textured glass is smooth on one face and figured on the other. Which way out is a real decision, not a detail.

• Texture facing out catches side light and gives the panel life when it is not backlit. It also collects dust, which matters in a kitchen.
• Texture facing in leaves a smooth, cleanable outer face and diffuses whatever is behind the panel more strongly.
• Hammered and granite textures obscure heavily: good for privacy, bad if there is detail behind them you wanted to keep.
• Seedy glass, full of small bubbles, does almost nothing to privacy and a great deal to sparkle.

Whichever you choose, choose it once and write it on the pattern. Mixing faces across a panel is visible in raking light even when you cannot say why.

• Is the sheet big enough for the largest piece with the grain running the right way? Check this before buying, not after.
• Are there bubbles, stones or cracks in the area you need? Hold it to the light and look at it rather than through it.
• How does it cut? Dense opals and heavily textured sheets run less predictably. If the design has tight curves, spend them on a well-behaved glass.
• Can you get more? A panel finished except for one piece of a discontinued sheet is a particular kind of misery.