Making a light shade from conduit

Stacked increases / decreases part 2

My attempts to create an interesting fabric using stacked increases and decreases are bearing fruit.  I’ve produced something with a lot of strange, teat-like structures, like the underside of a sow.

Stacked increases and decreasesThis might have possibilities for a ski hat, say, or a scarf, but it’s not what I’m looking for. But this is more like it – interlocking shapes in a flat fabric.

Stacked increases and decreasesMore work is needed to work out how best to fit such shapes together.

I was wrong, last week, when I said that the formulae used to derive the instructions for a particular number of increases or decreases came from The Interior of My Brain blog. No, I found them instead on the blog of the designer of Fox Paws, Xandy Peters.  Credit where it’s due.

Making a light shade

Since redecorating our bedroom last month (curtain hems not all finished yet, but let’s not dwell on that) I’ve come to the conclusion that the ceiling light needs a more exciting shade.  As a temporary measure, I painted the old coolie shade in a slightly darker shade than the walls – I knew all those tester pots of emulsion would come in useful.  The only problem is, I did exactly the same thing when we last redecorated the room in 2001 and never got around to replacing the shade.  Goodness knows what colour it was to start with, I can’t remember, but it must be more paint than fabric by now.

Well, I don’t want to be painting this shade yet another colour in several years’ time, it’s long past its ‘best before’ date.  With that in mind, I started work on a replacement this weekend.  We have a lot of PVC electrical conduit of various shapes and sizes in the garage (doesn’t everyone?), because it comes in long lengths and we only ever need a foot or two at most.  There’s also a nearly full pot of the solvent-heavy glue that is meant for sticking the conduit into elbows, bends, connectors and other fittings. Surely I could make something from these leftovers?

I turned to Instructables for inspiration and found this PVC Light Shade tutorial.  The author has used an inflatable beach ball as the former for a globe-shaped shade.  I bought a beach ball on Amazon a couple of weeks ago, all ready to make a start when the weather got warm enough to work outside.

Unlike the Instructables original which used only circular section conduit, my shade will be composed of flower-like elements made of slices of both round and oval conduit.  I also have some narrow, self-adhesive copper foil from a foray into making Tiffany-style stained glass creations circa 1994 – that needs to go too.  If I stick a length of the copper tape inside each circular slice of conduit, that should give the shade a bit of sparkle and make it more interesting.

I got out the Dremel this morning and tried to build a jig that would allow me to slide or swing it out of the way easily while I removed each slice and butted the remainder of the tube up to an end stop, ready for the next cut.  But I failed miserably, our hobby tool is actually a Dremel knock-off and it’s all curves with no means of clamping it easily.  My dear husband came to have a look at this point and, amazingly, offered to cut up the conduit by hand using a mitre saw.  I gave him a spec of 5.6-6.0mm slices (the copper tape is just under 5mm wide) and, after a few hours of sawing, he has produced about 30 round slices and 80 oval ones.

Flower arrayTo find out how many we’ll need, I blew up the beach ball and measured its diameter – 33cm.  Then I laid out a flower array of one circular slice and 8 oval ones and measured its diameter – 6.6cm.  For a rough idea of the number of such arrays required, all that was then required was to compare their surface areas: 4πr2 for the sphere and πr2 for the circle.  To my great surprise, the answer (4 x 16.52 / 3.32) came out to a very round number indeed, 100. Had I stumbled across an unfamiliar Pythagorean triple? But after a moment’s thought and realising that 33 is a multiple of 6.6, I saw why the answer was 100:

4 x 16.52 = (2 x 16.5)2 = 332

and 332 / 3.32 = (33 / 3.3)2 = 102 = 100.

That means the shade will need 100 circular slices and 800 oval ones, plus some extra circles to fill in the gaps between “flowers”.  I’m keeping quiet about that for now.  I have a nasty feeling I’ll need to buy more conduit, which rather defeats the purpose of this project which was as much to clear out Stuff as to make a new light shade.

Copper foil in ringI’ve tried sticking the copper foil inside a ring and it wasn’t easy.  But it doesn’t look too bad.

About yorkshirecrafter

I live and work in West Yorkshire.  I've always enjoyed crafts of all types, from woodwork to lace-making.  I also enjoy anything mathematical, which makes knitting a favourite pastime, especially complicated designs.  I've been advising businesses and industry on environmental matters for 30 years and also have an interest in green living, especially where it saves me money. I live with my husband and our Maine Coon in a 100-year-old cottage that constantly needs something doing to it.  Fortunately, I enjoy DIY too.
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1 Response to Making a light shade from conduit

  1. MrsCraft says:

    I’ll be watching your lamp shade progress with interest, it’s a really clever idea! 😊

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