Wednesday, May 11, 2011

Leather Bead Caps- Some Math Involved

Ive been in desperate need of bead caps lately, but I don't like my jewelry to have the same look as everyone else who bought their supplies at the local bead shop. So I often buy vintage and antique pieces. When I cna't find any that will do I make my own.
My DH has a pile of leather scraps from an abandoned hobby. I remember seeing a demo on making leather flowers on Youtube. When you burn the edges of your leather flowers the petals curl and cup.
I thought this method of shaping leather might make a promising alternative bead cap as well.

Here are instructions based upon how I created them.
To begin with draw three 25mm circles on some leather from 4-5 oz leather. These will be your test pieces to determine shrinking.

On your leather draw a line left to right in front of you then left to right on your circles. This will show you which way your leather is facing after burning so you can determine shrinking percentage correctly. Your leather will not cup and shrink evenly. You can skip calculating and testing if you feel lucky, but in my experience (and experimentation) most leathers will not shrink evenly. The larger a piece you torch the less noticeable distortion is.

You will want to torch your leather outside or under a vent hood because it can get smokey and smelly as it burns. Now lay your leather circle on a piece of fire brick or unglazed bisque tile, with the lines you drew on it facing down on the tile/brick. Un-lined side facing up.
Carefully torch the edges in a circular motion until they begin to curl up and your circle becomes an oval cup shaped cup. I'm using a small propane jewelers torch in the video below.

Clean your test pieces in warm soapy water and 'work; them by bending them inside out the right side in over and over until they soften up. Reshape them and let them dry completely. Then measure them in millimeters so you can calculate how much they shrank.

Now determine how much your leather shrinks on each side.
 Here is a formula you can use:
(new width/original test circle size) = new size in percent
(new length/original test circle size) = new size in percent

percent reduction in width- 100% = percent shrinkage of width
percent reduction in length- 100% = percent shrinkage of length

How I applied it:
20/25= 0.8 or 80%;  80-100 = 20% shrinkage of width
15/25= 0.15 or 60%; 60-100 = 40% shrinkage of width

Take the average of the three test pieces and use this as your percent for the rest of your calculation purposes.

So now I determine oval sizes that will shrink and curl to approximately a circle when I torch them.
15mm circles = (15 x 20%)+15 width x (15 x 40%)+15 length oval
or   15mm circles = (15 x 0.2)+15 W x (15 x 0.4)+15 L
this gives me a 18mm wide x 21mm long oval that will become (roughly) a 15mm circle once the edges are torched and curled.

After determining several sizes I went into Photoshop and began making oval templates.
I made the following templates:
15mm circle = 18mm x 21mm oval
20mm = 24mm x 28mm
25mm = 30mm x 35mm
30mm = 36mm x 42mm
35mm = 42mm x 49mm
40mm = 48mm x 56mm

Here's my template. 'Grain Direction' is actually the direction with the most shrinking.

Now use your templates to trace and cut new ovals.
Once your ovals are cut find the centers and punch a hole in them with a leather awl.
Torch and clean them just as you did your test pieces.

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