Monday, July 17, 2023

New Fountain Version In Jesmonite

Having arrived at the decision to cast a new version of the fountain in Jesmonite rather than the other options; (a completely new work, a repaired copy in bronze, repair the existing with a composite or do block marble repairs etc.),  I decided that key features need to be recorded before it was dismantled, so I used putty rubber to make an impression of faces, hands and feet. See the blue bits in the photo below.

The structure was successfully dismantled and delivered in bits to my studio. 

I needed first to remodel the existing marbles without further damaging them.

I used an oil based clay and started with repairs to the sea dragon’s head and body. Then I moved onto all four figures which needed four new faces, then body rebuilding including eight feet, eight hands - two of them clasped together, lots of hair and two completely new arms. Here above is the top figure ready for the client’s view. 

Then came the tricky bits. 

First of all, it was decided later that the old bowl was not fit for purpose and could not be reused because it was damaged and really would look aesthetically very different to the new figures.

Secondly, according to my helpful sources of advice, the use of Jesmonite meant that any mould would have to be especially sophisticated with a minimum of seams as the hiding of seams in the cast would be extremely difficult.

From my extensive research, I had been convinced that Jesmonite was the best material to use. It was green, strong and durable and produced such excellent results aesthetically.  However it seemed that no one had actually done something quite like this before. I knew that just about every garden centre in England had a cast of some 3D figure in a white composite substance which must have been cast from a mould. So turning out a Jesmonite marble was perfectly doable and I was learning a couple of useful tricks, vibration to remove bubbles when mixing Jesmonite and the use of a trowel. 

As a sculptor principally in bronze and resin bronze, I have significant experience in doing one piece silicone rubber moulds for the production of 9 casts to fit the ‘Fine Art’ definition of my work. Resin, like Jesmonite is even less tolerant when it comes to seams. It is nigh impossible to hide a seam in resin bronze if it is traditionally paternated. 

The top figure, with his interesting Sea Dragon, was relatively easy to mould and cast and needless to say I did him first. The second attempted cast was a success, I learnt a lot from the first and I lost no sleep worrying about it. 

The problem on the first cast was caused principally by my inexperience of Jesmonite and its available working window; Jesmonite goes hard (cheesy) very quickly indeed. I needed more time, lots more time. This was solved when I  got some good advice from Jesmonite themselves. Super Plasticiser, a second additive would keep it more liquid for much longer so helping the pouring process. My supplier had advised one additive Retarder which had given me about 20 minutes to work but Super Plasticiser more than doubled that and the two additives together made it much more liquid and so far easier to work with. Jesmonite also informed me that these additives would improve durability even more.

At this stage my clients, the committee, came to visit to see what I had done so far. The top figure with Sea Dragon was looking good and I could demonstrate that Jesmonite shone, sparkling beautifully in the sun. My work on the other figures was progressing well and they left my studio  very happy indeed.

My next problem was to mould the bowl. It had been delivered on a pallet and was incredibly heavy. I bought a pallet truck on eBay but the bowl needed lifting so I could place a sealed piece of plywood under it as a base for the mould. A friend and neighbour came to the rescue with his JCB so I was able to construct the mould. Another friend and neighbour made a wooden frame so I could work the cast the other way up.

From the above photos, including the casting, you can see it looks quite heavy! 

You may remember that March and April 2023 were very cold and wet. Jesmonite has to be stored above +5C and wet is not recommended! Tricky storage challenge solved by me taking over the outside shower and laundry - I was not popular!

One potential issue I had been told to watch for was cracks. When drying and exposed to sunlight others had experienced cracking, presumably splits in the casts later in the process. This was not my experience but I was careful not to expose the casts to extreme or rapid temperature changes which may have averted this issue.

The only cracks I found were in the jesmonite AC100 which I used for the outer shell of the moulds. They were expected in the nature of shell construction and easily mended. None of the casts however, as I have mentioned, showed any cracks when they left my studio nor on inspection in July. 

My next and final task was my most challenging. A one piece silicone rubber mould of three figures around a central decorative column. 

Although I think I knew all the potential things that could go wrong there is always the chance that something actually would. In fact it was only the weight of rubber, shell and subsequent cast which proved to be difficult. Like the bowl it was all very heavy and the use of ropes, beams and stack trucks were needed with friends lending a hand that saved the day. My solutions to the problems of weight all look rather ‘Heath Robinson’ in these pictures but they worked!

I needed eight walls and a similar number of plugs. This is where preparation of the original and filling awkward areas of the silicon rubber mould made the whole thing possible. (Next time I will use more keys in the rubber base area).

I was very careful to be as accurate as I could in mixing jesmonite. I used a drill to mix the base, liquid, plasticiser and retarder and a drill to vibrate the mixture to remove bubbles before pouring.

You will have spotted in the pictures that some pipe work had to be incorporated into my casts.

Here is the result:

Raining again!


Jesmonite is a great material to work with. Yes you can hide seams but keep them to a minimum if you can. Yes you can sand it, fill holes, strengthen it (with chopped strand mat after mixing), and protect it from stains. ‘Acid etched’ and it will shine better than marble. It needs some care and maintenance to keep it looking good. However, all outside Art needs to be maintained when exposed to weather and climate. 

Look after your art and it will love you too.