Density matters

Well I am slowly learning the importance of density. Density differences is what allows oil to be separated from water, allows cyclone vacuum cleaners to work and make sponge cakes light and airy. I never imagined it would come into felting.

When I talk about density. I mean fibres density , measured by me in mg/cm2. Not the same units as you would measure the density of an oil or air. So why does the fibre density matter.? Well first you lay out your fibres before felting , thinly or thickly, two , four or more layers and this is the starting point of the final density. Then you felt , and effectively the gaps between the fibres shrink , the overall area of the felt reduces and the fibre density increases. The more you felt , the denser the final piece is. Exactly the same as boiling a sauce to make it thicker or more dense.

Why am I even discussing this. Well I made a piece of felt to show the migration of dark and light fibres into colours. Sounds simple but I thought it looked terrible. The fibres did not seem to migrate and I felted and felted until I had a stiff inflexible piece of felt, like a small doormaat. I felted another piece testing out a few pieces of prefelt I had made and it was lovely , fibres migrated and piece was soft and flexible.

What was happening?

My first piece started with 36 mg/cm2 of fibre and ended up after 56 % shrinkage with 81mg/ cm2. My second one, started at 20 mg/cm2 and finished at 33mg/cm2, with 40% shrinkage. Less than half the density of the first. The first far to dense , the second if I am honest not dense enough, as it has some very thin patches when you look at it. All these density figures disguise thick and thin patches as they are only averages. Very tetchy I am sorry!

So I designed a third sample. I want it to end at 40 mg/cm2 with 40% shrinkage and a starting size of 30 cm X 30 cm. So I needed 22g of fibre to start . Divide in three layers , the bottom two made out of three different colours and the top one , out of six. Well this is a challenge for the sensitivity of my kitchen scales. So it was all bit approximate, but I think it worked.

Start point mini rainbow door mat

Final flexible Fibre Rainbow

Both samples show if you look carefully the migration of the different coloured fibres from underneath.

You know I think there was a lot of information about this in my course notes, but I guess this is one of those things you have to lean for yourself.

 

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