Final Week: FINISHING PROJECT

I glazed my bowls on Monday this week. This required a lot of concentration! Firstly the glaze had to be mixed around a lot, just before application, as the heavy copper in the sediment was quick to separate and would settle at the bottom after only about 10 seconds of being undisturbed. Once filled and left for 8 or 9 seconds (a time found through trial runs) the glaze left over after pouring out the rest was tested for thickness by ‘scratch testing’. Leaving them to dry for about 40 minutes helped make them absorbent again for the outer glaze – I used the spray booth for this, which was SO MUCH FUN. When switched on, the back becomes a waterfall to catch the excess glaze spray droplets. By slowly rotating the bowls, individually propped up on a rest on top of a wheel, I was able to obtain a really even transparent glaze for the undersides. To leave a surface glaze-free to rest on whilst firing, I wiped the rim of each bowl with a sponge. They were fired that afternoon and came out on Wednesday. This meant I was only able to mix up a paint colour on Wednesday after seeing the colour of the finished oatmeal green glaze, so this meant the doing final layer of paint cut it fine on time available.

Creating the platter itself was fairly easy – the model was made using the laser cutter, and the output file on Illustrator that I used only needed a bit of tweaking and scaling up. The model, being on the 1:10 scale, would have been scaled up to 1m in diameter. I decided that (since making the bowls) this would be too big, and although I wanted the platter to be something decently sized that you could rest other things on, this would have been a bit too large for most room settings. I reduced the dimensions to the following:

  • Outer edge diameter: 80cm
  • Inner edge diameter: 50cm
  • Bowl slots diameter: 5.8cm
  • Depth: 1.5cm

I wanted the table itself to feel substantial. I didn’t want it flimsy or breakable, as that would make people nervous around it – the opposite feeling to what I’m trying to create! The bowls themselves also had to sit well in the slots – they couldn’t be too small, as otherwise they would tip about and be prone to falling off (not good). The largest diameter which would keep them all from falling through was 6cm, so I lowered this and went for the slightly smaller option to account for any more shrinkage in the last firing.

I had the final design cut on the CNC machine. The machine had to leave gaps in the path it cut; if it cut a complete circuit, the pieces might move around a bit, potentially messing up the cut. It leaves small gaps in the path which have to be chiselled by hand afterwards, to remove the pieces. This is tricky to do without taking little lumps of MDF off the bottom surface. Next time I use a CNC machine on MDF, I will know to really whack down the chisel with the mallet, sharp and fast! MDF is made up of layers of pulverised wood, and can easily peel off bits if not cut cleanly.

Tuesday and Wednesday were set aside for painting the platter and finishing off sketchbook work. Painting MDF is tricky, as it soaks up the paint very quickly – in order to get a smooth finish on the edges, a number of layers are needed. I used a combined Primer & Undercoat (white) for the first layer, applied with a roller for a smooth finish on the top and bottom sides, and a brush on the rough edges. The MDF just drank it all up! Another layer of undercoat was therefore required. My time plan for painting helped, but it didn’t match up perfectly… A time plan for any painting is a seriously useful thing, if you know the drying times. I did know the drying times, but had to fit in more layers due to the thirstiness of the MDF. That’s certainly a learning for next time, too. The final layer was a mixture of two old gloss paints I had lying around from other projects, I mixed a few drops of a burgundy -sort of colour in with a teal blue/green which was slightly too much on the light and green side. The red was not mixed by hand, it fit in with the mood board as well as complementing the reddish-pink of the design on the underside of the bowls.

The previous week, I did some calculations to work out the length of nylon cord needed and whether or not it would hold the platter safely (without stretching or reaching breaking point – the ‘upper tensile strength’ if you want the proper name!). The nylon cord is far more than strong enough – the maximum tension in each cord would only be about 4% of the maximum safe load on the nylon. It is now ready to hang in the exhibition.

In hindsight, I wish I had left more time to let the paint dry, just to have avoided the stress of this week! That would have meant starting the bowl-making process a couple of days earlier and making the final details time plan from the moment I started throwing the bowls.

 

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