(Fig.4. Broken bottle taped back together.)
In order to make the mould, which I did once the cracks were resined, I used a two part silicone mix, one part silicone to one part hardener. Once mixed together they set within five minutes. This particular brand was called 'dentasil light' and was used in dentistry. Once the glass was clean the first step was to pick another part of the bottle which mimicked the contours of the area I wanted to fill. I then spread the silicone mix onto this in a square shape larger than the hole and in a consistency thick enough to be easily handled without it coming apart or losing its shape.
I repeated this process twice, once for the shape of the inside of the bottle and one for the outside. The silicone I spread on the outside I did in the same way with one exception. I held a small section of drinking straw onto the glass firmly while I pasted the silicone around it (this is easier with two people). This was done so that once it was set the straw would act as a funnel I could inject the araldite into, and also act as an air vent to release any trapped bubbles. In larger moulds you will need two straws one to act as an air vent and a separate one to pour but because mine was so small this wasn't an issue.
These two mould sections are then stuck to the inside and outside of the site needing infilled in turn. They are fixed using extra silicone which is applied thinly with a finger around the edges of the hole, being careful not to get any into the area for gluing, and the mould
(Fig.5. Mould made of dental silicone with straw)
is then pressed into it until set. This was a fiddly business for me because it was very hard to get my hand far enough up the bottle to do this at all never mind doing it with any delicacy. It is very important that the silicone mould is stuck firm otherwise the araldite will seep under it, the mould will fail and the after effect will be very hard to clean because it is so hard to get to. I found this to my peril on my first attempt. It is also worth noting that once the mould is in place the araldite must be applied very slowly so as not to create bubbles, a little at a time. The longer it is since you mixed the araldite the thicker it will be and thicker glue creates more bubbles because the air finds it more difficult to escape. If bubbles do occur, rock the glass from side to side to try and chase them up the air vent. If this doesn't work, or you can’t see them because the mould is not clear then use fresh araldite and hopefully they will rise to the surface. Surface bubbles can be easily filled in once the glue is set and become invisible.
Although in the end my infill worked, for the sake of experimentation I removed it in order to do it again using an alternative method. This time I used wax. It works on the exact same principal, one piece inside and one outside. Although instead of the straw you cut a small hole. At the university they had a special little drill to do this with but I imagine you could do the same thing with a sharp pencil. Where as in previous studios we always used a hair-drier to soften the wax here they had another special tool. I used an electric metal spatula, plugged in like a soldering iron, which when heated could be pressed into the wax to seal it to the glass. This of course was accidental, because I could never have fitted a hair-drier into the bottle. This time I had premixed powder pigment into the araldite so that when I added the hardener I was able to perfect the colour by adding a little blue and a little yellow to create the olive green of the bottle. I injected this a little at a time through the hole in the wax and into the cavity, swaying the bottle to let the liquid
(Fig.6. Alternative Wax Mould)
reach the corners first before adding more so as not to get bubbles. Once hardened I felt that this method had worked very successfully and I found it easier personally to use the wax rather than the silicone.
The final item I had to break and fix was a lightbulb. This process was exactly the same as the others. The curve of the surface made it marginally easier the fit the pieces back together but many were so tiny, the glass so thin and fragile, that it really was an extremely difficult job. In the end I had to glue one half before I could continue reassembling it because it was so delicate that even with tape it kept coming apart in my hands. The final pieces were so small they had to be fitted using tweezers and the task was so arduous at times that it seemed like it was un-accomplishable. I did witness another student finish one, so I can testify to
(Fig.7. Taping broken lightbulb)
the fact that I have seen it done and it is therefore possible, but as I had such a short stay there I will admit that mine got the best of me and was never fully realised.