A guide to assembling fossil jigsaws!
I prepared this fossil several years ago for a friend. It’s a good example of a fossil jigsaw, not all fossils can be extracted in one piece due to the nature of the matrix they are found in. There are many different states of preservation and many conditions that affect the solidarity of the matrix from burrowing sea creatures such as piddocks to storms, moisture heat etc. However, despite all these factors, fossils often can be glued back together perfectly as long as the joins and edges of the rock are clean. Stone glues are available in many different colours and either thin or thick consistency.
A good practice in the field, when collecting a fossil in many pieces, is to localise areas in small bags. This will make the piecing together easier, as you will have fewer options to try when assembling. If the pieces are all put in one bag and mixed up, the locating and glueing will be very complicated and time-consuming.
Once the pieces have been dried slowly over the course of a few weeks, I arrange the pieces on top of newspaper. Glue will inevitably seep through between the gaps, so to prevent glueing the fossil to the table or in this case the floor, the newspaper works well, as it can be easily removed from the fossil after the glue is set.
I also dry test the joins first before adding glue so I understand exactly how the two surfaces join up. Once I have offered the pieces together, I draw location lines across the joins, this helps to visually line up the rock. If using superglue, you don’t get much time to adjust for errors before the glue sets!
If something hasn’t been lined up accurately and the glue sets, you can submerge them in acetone. This will melt the glue which can then be scrubbed off with a tooth brush, once dry you can then glue them back together perfectly. Any loose fragments should also be removed from the edges before attempting to glue as they will often hinder a perfect join.
It can also help to prepare some of the fossil before joining them as the various shapes, in this case, bone, make great location markers.
Sometimes due to the weight of the rock, it’s a good idea to add some temporary metal supports. In this case, I have cut some coathanger wire which is very strong and positioned the cut lengths over the joins. This helps strengthen the joins, allowing you to handle the rocks later, reducing the chance of the weight of the rock snapping the glue line. At the end of the process, I will back the whole fossil with fibreglass, which will make the fossil a strong and stable piece.
I add fibreglass resin to fill the glued cracks and joins, this can then be sanded later and blended to resemble the original matrix.
The bones are then coated with a weak solution of paraloid to protect and bring out the colour and contrast of the fossil.
The fossil is finished. It’s strong and light enough to be easily displayed on the wall if required.