Darren Tanke’s Gorgosaurus preparation 20: fixing undercuts, the final preparation

The last of the Gorgosaurus preparation (on this side) was finished February 10th. In readiness for molding, holes, cracks and undercuts have to be filled and this phase is rapidly reaching the end, too. The plan to mold the edge of the field jacket as well means the edges between the cut part of the plaster jacket and the rock itself needs special treatment.

The plaster jacket was of course made in the field with no advance knowledge that it would be molded in part later on. So these edges need to be fixed. They are rough, full of undercuts and often form vertical faces that are harder to fix to make look like rock. Most of these problematic edge areas are simply glued and crushed sand and silt thrown against the wet glue. Once dry, excess sand/silt is vacuumed off and the process repeated up to three times until the white plaster is hidden by simulated rock. Undercut areas on the edge of the jacket are fixed by using the glue/sand/silt mix which is roughly pressed into the undercut or hole, then sprinkled with dry sand/silt which is then firmly pressed (with the heel of the hand) into the damp glue/sand/silt mix underneath. This is done for any other gentle depressions or undercuts: a series of pictures are given here. Once dry the effect is quite realistic. Also, any remaining cracks are being heavily glued. I try to do heavy gluing jobs on a Friday afternoon- this way it has all weekend to dry without any disturbances from me. Come Monday morning everything has firmly set and the process begins anew until everything is done. Vertebrate paleontologist Philip J. Currie is to visit our museum (and see the Gorgosaurus) for the first time on February 18th so it is important that I be done by then.

I must apologize to readers about the image quality. The specimen, when seen in person, is really quite spectacular- the bones have a beautiful chestnut-brown to orangey-brown (more heavy on the orange) and all with a deep, rich lustre. These color qualities, which really make the specimen all that more amazing I have found very difficult to convey photographically. The overhead lighting near the Gorgosaurus has been changed this week which also has affected image quality.

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

Late edit: Matt van Rooijen has done a colour edit on that last image to try and perk it up a bit:

4 Responses to “Darren Tanke’s Gorgosaurus preparation 20: fixing undercuts, the final preparation”

  1. 1 kattato Garu 14/02/2011 at 12:16 pm

    What a spectacular specimen. I don’t think you had posted one of the whole thing, had you? My question then – how much of this was visible in the field, did you know how much you had or did you have to guess at the total area to be jacketed and lifted… and how much does it weigh?
    Congratulations on a fascinating series, I’ve REALLY enjoyed it… so far!!

  2. 2 Darren Tanke 15/02/2011 at 3:26 am


    I found this specimen during the last 40 minutes of the last day of the field season. Sometimes things happens this way. Not much was showing. I saw a shattered tyrannosaurid limb bone, an unidentified bone and belly rib pieces (plus a partial hand claw and another hand bone) on the slope downhill. All tyrannosaur and all small indicating a small animal. The belly ribs still in the rock formed a line with the other larger bones (over a 2 metres distance) suggesting much of a skeleton was there. I had a “good feeling” it would be a nice specimen. It had likely escaped being found by others as a soft iron-rich layer above had been eroding and pieces of this were largely covering the line of ribs. We uncovered a small area. It did not take long to figure out the rough outline of the skeleton. The block weighed about 1,000 pounds (~500 kg) when it was helicoptered out. It could have been dragged out like they did long ago, but that would have endangered the skelelton inside. Glad you are enjoying the posts.

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