Darren Tanke’s Gorgosaurus preparation 17: supporting the breaks

The last of the preparation is now being done on the Gorgosaurus. Several bones were completed on January 19th. These were the first ones to be completely finished. The nature of the rock is cracked and crumbly and despite best efforts, some rock along the edges and underneath the bones has fallen away. The bone is not properly supported and the missing rock needs to be replaced. The femur was badly affected this way. To remedy this (shown in a series of 4 pictures), I mixed some thick glue with sand from the Gorgosaurus block. Waste rock was broken up and ground into sand and dust, using a short length of a hardwood broom handle as a rolling pin. The resultant sand/dust was poured into the jar of glue and stirred together. The result was a thick paste which could be made more runny by adding more glue, or thicker by adding more sand. This paste was applied to the undercuts using a small metal spatula. Because the paste was so thick, it was easy to work and retained its shape. It dried hard in a couple hours and the bone is now safely supported. The support can be removed in the future if need be by squirting acetone onto it and removing the resulting paste. Also, once the paste is hardened, it can be shaped with an airscribe if needed. The final result is quite convincing as “real rock”.

The final treatment of the completed bones is a very thin coating of glue, made so thin that it does not sit on the bone surface, but soaks in. It seals up any remaining microcracks and dissolves and old glue on the surface. The provided picture with the brush shows part of the now fully prepared ischium, with the surface treatment of glue. Final preparation of the rest of the skull and skeleton will go quickly now.

All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.

7 Responses to “Darren Tanke’s Gorgosaurus preparation 17: supporting the breaks”

  1. 1 A.Gaeta 21/01/2011 at 4:25 pm

    As someone that is planning to prepare fossils herself in the distant future, it is interesting and quite cool to see how such an act is done. Thanks for the blog entries!

  2. 2 Mark Robinson 22/01/2011 at 9:52 am

    Thanks again, Darren. Quick Q – you mentioned that the “pseudo rock” support can be removed in the future, yet you also said that it is quite convincing as “real rock”. How difficult is it to tell what can be removed with acetone and what will require something more substantial?

    • 3 Darren Tanke 22/01/2011 at 4:56 pm


      Good questions. I think you are asking how will someone be able to determine what is the fake rock vs real should they choose to remove the former later on. The fake rock needs acetone to soften it up, but I suspect it can just be airscribed away if need be. I have already textured and shaped some of the fake rock with an airscribe and it was done easily. Before the specimen is latex molded, ALL the rock has to be glued too, so it does not pull apart when the latex mold is removed. But I don’t anticipate problems there either. One potential problem in the future is someone being able to tell my fake rock from glued normal rock. They do look much alike. To resolve this I will take pictures of the affected regions, print them off and label the pictures, showing where the fake rock is and my recommendations as to how to remove the fake rock (what solvent is required, depth of fake rock, etc). These pictures will be put in the paper catalogue records of the specimen in our collections department. I may also leave a note inside a sealed ziplock bag against the specimen before I do a major support jacket and flip the specimen over so I can prepare the other side. If the specimen is ever flipped over again and my support jacket removed, they will find my note which will recommend what solvent they need to dissolve the glue I used in the fake rock and alert them to the fact that there are pictures showing what rock is fake with the paper catalogue records. Little notes like this take only a few moments to generate yet often “save the day” years later when an unexpected question or situation arises. I only wish my labmates did this more often.

  3. 4 Darren Tanke 22/01/2011 at 5:00 pm


    I should also add that as my fake rock is performing a critical fossil bone support role, it is highly unlikely it would ever be removed at all.

    • 5 Mark Robinson 23/01/2011 at 7:11 am

      Thanks very much Darren. All of what you say regarding taking photos and leaving short notes is obvious to me (I do similar things in the course of my work) but I know from experience across all walks of life that very few people take the small amount of time necessary to do these helpful things. I share your frustration regarding co-workers not doing this too.

      Just a small clarification – do you normally create this fake rock as a matter of course during specimen preparation or only when you think that it may be put on display?

      • 6 Darren Tanke 23/01/2011 at 8:18 pm


        We prefer to use the real rock whenever possible. It was difficult to do so in a number of areas with this specimen. The fake rock can be used either way- for regular preparation or for specimens going on display. You asked if I “normally” create fake rock and the answer is no. In fact, despite a 32 year professional fossil preparation background (and about 7 before that as an amateur)this was one of the few times I did use it and the first time using rock dust and sand mixed with glue. Prior I used plaster of paris which was then textured, painted rock color, glued, and sand thrown onto the wet glue in enough layers to look like rock. This time I tried something different. We are always reinventing ourselves with new tools, techniques, and procedures.

  1. 1 Darren Tanke’s Gorgosaurus preparation: final roundup « Dave Hone's Archosaur Musings Trackback on 22/02/2011 at 9:00 am
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