I usually help Peter out making bits and bobs for some of his great finds and a pleasure to do so. When he asked me about the Topf mine it looked like an easy challenge just glue it together and fill the holes, done and dusted but when I got it, it was another story.
Upon examining the mine it was a perfect mint example on the top and would have been underneath but unfortunately the bottom was badly smashed. I knew it could be fixed but it was going to be a long job and a difficult on of that. Luckily Peter sent all the broken bits and the glass plugs and fuze plate.
Most people think and it is said in some books about mines that the Topf mine is made of plastic or a Bakelite but its not, its made of compressed wood chippings, mixed with a bitchemen or tar compound, a bit like a coal like digestive biscuit, when broken, delicate and crumbly (but not to eat). So imaging gluing up a mine shaped digestive biscuit, the broken bits crumble in your hands etc. I also had to workout and experiment with glues to put it together and a filler to fill the large and fine gaps, cracks and holes.
I first thought of araldite and superglue but a didn’t want fast drying glue or a glue that could affect the tar like material with the chemicals involved with araldite even though they may be alright. I also needed glue that would not dry out etc or would absorb into the mine material as it was quite dry. In the end I used wood glue PVA, as part of the material was wood. I could also pre-coat the joins using PVA watered down.
When I started to glue the bits together I found that it was not a simple glue bit by bit job, I had to glue three or 4 bits in one go, as the nature of the break was not strait forward. The bits interlocked ie I glued the first bit but the third bit wouldn’t fit in, I had to move the first bit to get it to fit etc etc. Then I had to support the parts while the glue set over night as well as check that the outer parts were level with the rest of the outer body. I had to do this many times until all the bits were in place bearing in mind that the bits were very crumbly. When the mine was all glued up it was surprising how very solid it was.
Next I had to fill the gaps and cracks. The material when broken didn’t leave a clean break, they had to be filled. The material used was again using PVA mixed with sawdust and black powdered paint that made the perfect filler and dried to a hard compound and blended in perfectly with the outer finish without using any paint or finish to touch up. The screw threads on the plugs were basically missing so I waxed the plugs with a spray wax and filled around the plugs in place, when the filler was just about set I unscrewed the plugs leaving a threaded part, the plugs could screw into. The main centre fuze threads were much better and there were missing parts of the thread, so I filled in these bits and re screwed the main fuze plug to form a thread in the missing areas. When dried I re screwed the plugs again so there were no tight spots, I didn’t want the shell to collapse again or crack in places under the strain. For good measure I mention to Peter that it would be a good idea to support the centre body so the mine wouldn’t collapse again for future preservation, it was suggested to fill in the mine voids with a foam filler but it was advised not to do so, as the force of the foam expanding could pop the shell of the mine, plus there could be a chemical reaction with the mine material in future days, I didn’t want it to crumble to bits or something similar, these are very rare birds Topf mines, so I didn’t take the chance. I also thought about filling it with polystyrene balls glued together but in the end I fitted a very thick cardboard tube insert, cut in four bits just behind the centre threads to the inside top of the mine. The outer shell filler was burnished down to match the rest of the mine, as you can see you can’t see the joins or the filler, only a camera flash will make it visible.
The sellers picture (a honourable BOCN-member) was showing a damaged back, but in all it seemed to be stable so far.
what a terrible mess, I was also really crushed! :tinysmile_cry_t3:
