Milk glass or similar

[Matty F]

I need a tube about 100mm diameter and 120 mm long, to go around this:

It's a heat sink for a 120 LED headlamp.

I want to diffuse the LEDs, but not with anything flat. I have a milk glass shade that has exactly the right light characteristics except that it's a big bowl about a foot across, and I want a tube with parallel sides. I don't want to cut out too much light, and frosted glass does not work. My house has milk glass lamp shades but they are the wrong shape as well. Perhaps white acrylic tube would be fine if I could find any. The headlamp doesn't get hot, only barely warm. I should think so too, with all that copper!

[alan]

If it doesn't get hot try a something like a plastic 2L bottle (cheap own brand cola/lemonade/water) with some stick on frosted glass film.

Milk is often sold in plastic containers that are semi opaque. The large bottles could be cut up to give you a large sheet which you could then form into the tube.

Some (food) liquids are sold in plastic containers with very colourful labels. The label is just a shrink fit plastic film which when cut (peeled) off reveals a semi-transparent thin white plastic bottle.

The UV from sunlight will degrade the plastic over time.

[Andrew Gabriel]

I can't actually see how it works, i.e. where the light comes from.

You could wrap tracing paper around it, perhaps with some white paper under it over the cylinder part if you don't want to see that through the tracing paper.

Any diffuser will lose you light, and something that looks milky when the light is off will lose you a lot, because it can only do this by not being particularly transparent and reflecting a lot of the incident light back out again.

[Matty F]

I have wrapped a few metres of white and red LED strip around the copper, which I have not photographed yet.

I do have a milk glass diffuser that works perfectly when it's about 10mm away from the LEDs, but it's far too big. It's off the interior lights in a tram about 80 years old and can't be bought any more.

[Nightjar]

Translucent silicone tubing might do what you want. Platinum cured, which does not yellow, is available in sizes up to 25mm ID. Try medical and food industry suppliers.

Colin Bignell

[Matty F]

Too samll, I need 100mm ID. However I have decided to use the large shade that I have. Here's the finished job, switched to red and yellow:

Here is the headlamp without the shade: