Bogie, the Bucket and the Bubbles

The good people of Stranraer have been puzzling over the hole-filled metal plate in the midst of their town since mid November - this is how it has looked since then

 

Or from the top of the Castle:

The next stage for this work was to fill the mould with a coloured concrete - just until the holes were filled flush with the steel. There has been a lot of head scratching about just how to do this...the weather enforced hiatus since November (too cold to cure concrete properly)has merely given us all more time to scratch heads and generally get anxious about all the potential pitfalls inherent in the operation.

Last Wednesday finally heralded a window of  +3 degrees centrigade for more than 48 hours. This is the story of the three days that followed:

Concrete poured into the holes in the steel from a readymix lorry (Luce Bay)

Bogie and Colin floating off the biggest of the 'bubbles'

Bogie doing the final finishing to the surface of the concrete from the bucket of the JCB -it was important that no one stepped on the steelwork during the pour as their weight was likely to bend the steel out of shape and create dips in the final surface

Halfway there - this is the beginning of the second half of the pour. The white pigment on the completed half is a sprayed on concrete retarder. This additive soaks into the top few millimetres of the concrete and slows down the setting time of this top section. The specified surface for the work was an 'exposed aggregate finish' meaning that after approx 24 hours the surface of the concrete would be pressure washed to remove the retarded layer of cement leaving the stone chips in the mix exposed.

 Final bubble being filled

 Alistair checking that the concrete has run consistently under the steelwork

 The surface after pouring and floating - we decided to leave it 'proud' of the steel so that it might finish up 'flush' when the top surface was washed away.

 The JCB bucket came in handy again for spraying the retarder onto the floated surface

 This is how the work looked the next morning after a first powerwashing to expose the aggregate in surface of the concrete. One of the great imponderables throughout was how to prevent concrete from sticking to the surface of the steel in the end we applied copious quantities of shuttering oil to the steel before pouring the concrete....as it turned out this was not very effective...we were now faced with cleaning back the whole steel surface.

 A few experiments revealed that scrubbing the surface with kitchen scourers and a weak solution of acid was the most effective method - this is the first patch we cleaned. Colin, Bogie and I spent many hours (and countless kitchen scrubbers) carefully removing the concrete from the steel.

This is how the work looked after the first 'wash-down' after a days scrubbing

 Close up

Another detail (the marking on the steel are areas of recent shotblasting to remove welding marks - in time these will oxidise to the same tone as the surrounding steel)

It is fairly normal for artists to be pushing techniques and trying something new - this whole work was an untried experiment on a giant scale. I am really interested and pleased with the result - but once again, in this odd public art world, the thing that I am carrying away from the experience at the moment is the way that skilled people can rise to the challenge of doing something they have never tried before and we can all work together as a team to get a result. 

Big respect to Davie Topping and his team - thanks all!