Bronze lintel

I was also making a bronze lintel. I had to take a silicon mould for the iron lintel so it was an opportunity to make one in bronze as well.

The process was much the same, but it needed to be made in two pieces because of the limit on the crucible size in the foundry. The mould was taken from the original wax and then a clever ruse with carpeting provided for the thickness of the metal. The photo shows taking the mould from the wax which has just been used for the iron lintel mould.

Eden (op cit) undertook the pour at SSW and welded the two parts together. I came in to fettle, chase and sand blast it. It is now at home in my studio awaiting final texturing and patina.

iron lintel casting

The day dawned bright and by lunchtime the mould was finally finished; Eden had mended the furnace and the ‘bull ladle’ was also fixed; the fork lift was in place to take the weight of the ladle; Michael had cracked the scrap iron (thanks Michael) and weighed the bags of coke and iron. Eden must have laid the bed of coke in the furnace when I was working on the mould indoors; the air blowers and gas tanks were in place. It was decided by the tech team to go ahead with the pour.

The furnace was lit and the air blower turned on to force the temperature up to melting point; the gas blower was turned on to the ‘bull ladle’ to heat it up ready to receive the molten iron when the furnace was tapped.

The photo above shows Michael adding a charge of coke and scrap iron to the top of the furnace. As the iron scrap heats it becomes molten and drops to the bottom of the furnace. When enough iron for the pour (over 65kg) is molten at the bottom of the furnace the bung is broken so the iron can run into the ‘ladle/crucible’.

The weight of the iron is taken by the fork lift and Michael and George manoeuvred the bull ladle into position and tipped it to pour the molten iron into the mould. There was a delay when the fork lift wouldn’t start and an alternative lifting device was tried before reverting to the fork lift.

 

Towards the end of the pour the bull ladle got caught in some way and the pour was aborted. The mould was showing metal through the air vents, so the general view was that the pour could be complete. The team have reviewed the equipment and made safety alterations since.

The metal needed to cool before I could peek inside, so I left it for the weekend. On Monday I removed the mould pieces to reveal an iron lintel, yeah

 

Thanks to Scottish Sculpture Workshop tech team and George Beasley.

Iron lintel – mould making continues

The silicon mould and plaster mother mould that I took on the headland at Clachtoll made it safely to the Scottish Sculpture Workshop for the next stages.

Firstly I re-constructed the plaster mould so that I had one complete cradle for the silicon. Then I pinned the silicon into the plaster support mould and coated the inside of the mould with wax. I stippled the first layer on to capture the detail and and subsequent layers were brushed on to build up a firm mould a centimetre or so thick (thicker at the top edge) I then built the wax up as far as possible to remove undercuts on the inside.

I removed the wax wax from the silicon ready to start taking the resin-bonded sand mould.

I built a temporary box and used petrobond sand to build up the base to the wax. I did not do a good job on this, so had to make extra mould pieces at the penultimate stage (note to self to do better next time).

The resin-bonded sanded is mixed and rammed into the box around the wax, taking care to avoid undercutting.

When the top part of the bonded sand mould was complete the whole box was turned and the ‘rescue pieces’ added. The base of the mould could then be made.

This makes a particularly uninspiring photo (above), but it over took a week to get there.

The mould came apart as planned and was built up into the base and the top parts. I cleaned the joins: Michael (SSW’s assistant technician) helped with the core wash; I found the bars to hold it closed and Eden (SSW technician) working with George Beasley drilled the pour holes and air vents; the piece was moved outside; the cracks were glued; the pour cups glued on; the clamp bars put on and it was ready to pour.

Unfortunately I only have video footage of this stage so I can’t show it. The next post will show the pour.