How to Specify a Custom Glass Lamp Shade: Measurements and Drawing

First inquiries most often leave out the quantity, the size, the tolerance and the color (SIGA, 2026). If a measurement is missing, the factory has to guess it, and the first sample can come back wrong. This guide lists what to measure, what to name and what to draw, so that the first sample is close.

Which measurements does a glass shade need?

A glass shade needs three numbers: the diameter, the height and the opening (SIGA, 2026). Our size chart shows where to place the measuring tape for each. State the unit, millimeters or centimeters, on the drawing, and say where the diameter is taken, at the widest point or at the rim. For a round shade, our globe glass lamp shades page shows the shapes to measure this way.

On the drawing, write each number once, with its tolerance next to it. ISO 129-1 sets out the general principles for presenting dimensions and their tolerances on technical drawings, and it points to ISO 14405-1 for what a tolerance on a size means. A factory reads a drawing laid out that way without questions.

What tolerance should I write?

Our molds hold a total error of 1 to 2 mm on diameter and height, and fully hand-blown shades about 5 mm (SIGA workshop estimate, 2026). Write the largest difference you will accept as a number within that range. These figures are workshop estimates from experience, not measured records, and the comparison of hand-blown vs mold-blown glass lamp shades explains how to choose between the two. If you need a tighter total error than 1 to 2 mm, say so in the first message so we can confirm whether we are the right supplier.

Which holder should I name, and how do I mark the opening?

Name the holder your lamp uses and mark the opening on the drawing: its inner diameter and its position (SIGA, 2026). A glass shade is hung or seated by its opening, so the holder decides the opening size. Our fitting guide lists what to send.

Send the holder drawing or a photo with its collar size. We drill the opening with a drill bit of the matching size (SIGA, 2026). If your holder is an Edison screw, name the base too, as explained in E26 vs E27; the number in E12, E14, E26 or E27 is the thread diameter in millimeters (Wikipedia).

What should the drawing show?

The drawing should show the shape, the three numbers, the tolerance, the color and the fitting. A side view with the diameter, height and opening marked is enough for a simple shape. For a molded shape, add a section view of the profile: in mold blowing the glass is forced against the inner surfaces of the mold and takes its shape (Corning Museum of Glass), and a full-size mold gives the object its final form (Corning Museum of Glass). Mark the color as a Pantone or RAL code, since we match those on request (SIGA, 2026).

The minimum is 20 pieces per design, so add the quantity (SIGA production data, 2026). Attach a photo of a similar shade if you have one. A photo does not replace the numbers, but it saves a round of questions.

Which gaps in a drawing should I check for?

Check four gaps that leave a factory to guess: a missing unit, a diameter with no point of measurement, an opening with no position marked, and a tolerance written as "tight" instead of a number. On a molded shape, a guess is costly, since the mold carries the shape into every piece.

Check your own sheet against those four before you send it. Then add the holder drawing: the opening depends on it (SIGA, 2026).

When is a drawing not enough?

A drawing is not enough if the shade has a complex shape and you also need a strict tolerance, because the process choice follows from both. In that case, send the drawing early and ask for process advice before you finalize the lamp (SIGA, 2026). We are also not the right supplier when the requirements are excessively strict, and it is better to find that out at the drawing stage than at the sample.

Frequently Asked Questions

Which measurements do you need for a quote?

The diameter, the height, the opening, the tolerance, the color and the quantity. State the unit on the drawing, say where the diameter is taken and which end carries the opening, and add the holder drawing so the opening can be drilled to fit it (SIGA, 2026).

What tolerance can I expect?

A total error of 1 to 2 mm for molded shades and about 5 mm for fully hand-blown shades, on diameter and height (SIGA workshop estimate, 2026). Write the largest difference you will accept as a number, because words such as tight leave the factory to guess.

Can I send only a photo?

A photo helps with the look, but it does not replace the three measurements. Send both, with the unit, the tolerance and the holder, so the first sample is close and the mold maker does not have to estimate the profile from a picture (SIGA, 2026).