This update covers November 10 and 12, the 11th being a holiday. Work has slowed down substantially on the Gorgosaurus project. At the beginning I was removing 4 trays of waste rock per day, now it is about 1 tray every 4 days. There are a number of reasons for this, all related to the specimen and, the matrix it is in, its fossilized condition.
1. I am finding the top and back of the skull is now what we call “punky bone”. Instead of being hard and well preserved (like most of the rest of the skull), it is now soft and has a consistency somewhat like rotten cork.
2. When the specimen was buried long ago, some tree branches were also buried with it. These in time fossilized into coal. This coal has now become loose so what is left is a hollow tube (representing the outline of the branch) with coal crumbs loose inside. Where a branch rested next to the skull, this means that now a hollow tube lies next to the skull. As you can guess, this is not very good support for the skull, so stabilization work proceeds slowly in these areas. Also cracks continue to be an issue, affecting much of the posterior half of the skull.
3. In other areas, the bone has shrunk away from the bone impression in the rock, so as you dig down, the rock suddenly collapses, exposing a hollow space. At the bottom of this hollow is the bone, sometimes OK, sometimes all jumbled up. In one area the jumbled pieces resembled a train wreck. What should have been a long smooth, continuous and slightly convex bone surface was now a jumble of pieces angled up and down and overlapping each other. Owing to shattered rock (and the bone) all I could do was glue the bone AND the rock so everything is one solid unit. Sometimes it is important to glue the rock too.
4. Palate bones and bones at the back of the lower jaws are paper to light cardboard in thickness. I can only expose about 1-5 mm at a time and glue that, then work elsewhere while that glue dries. Much work is accomplished daily, but it may not immediately appear so in the photographs posted over the past days. This is opposite to the pictures posted the first 3-4 days of work.
I am still trying to wiggle the errant, disarticulated right postorbital out. I am forced to dig down through the secondary fenestra in the maxilla (the smaller of the two holes) to exposed the end of the postorbital. One process of this bone is pinched between the two upper jaws but by micro-mining techniques I will be able to get it out. Soon I will begin to work my way down the neck and expose the vertebrae and neck ribs there.
One aspect of preparation I would like to cover in this posting is safety equipment, often overlooked. We at the Royal Tyrrell Museum take health and safety matters seriously. In the lab we provide all workers with eye protection, dust extractors, dust masks, hearing protection, and hand protection (padded glove) to protect against vibrations from the air scribes. We even have a corrugated rubber mat to stand on which help remove the strain of standing on a hard and cold concrete floor all day. We all have to wear steel-toed boots in the lab. Technicians use all or none of these safety items dependent on the work being involved. Different types of each are provided to suit their personal likes. There area also regular health and safety meetings (by a dedicated committee) and regular lab inspections.
More to come soon. All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.
Dave Hone's Archosaur Musings 
This series is fantastic. Profuse thanks for this insight on preparation.
Although it’s a setback from the earlier work, the problems encountered give non-palaeontologists like myself a good view of what van be encountered. Fascinating stuff, and I’m glad to be able to read it.
Kilian,
I am assuming your “setback” comment is in regards to the poor and cracked bone now encountered on the Gorgosaurus skull. Be assured it is not a setback to me personally or professionally. It is taken on as a new challenge. Even the best fossils in the best rock always have something “not right” with them and in these cases fossil preparators everywhere rise to the challenge and make the fossil right again so it can be properly researched and possibly put on public display some day. Glad you are enjoying these posts. I am glad Dave Hone gave me the opportunity to spell out all that goes on during the preparation of a fossil. Hundreds of thousands of Tyrrell Museum visitors look in the Preparation Lab window each year, but only spend a few minutes watching a process that is long-running and quite varied in its approach. This blog gives viewers worldwide and first hand and day by day account of fossil preparation- a skill often overlooked and underappreciated.
“a skill often overlooked and underappreciated.”
And that is really why I was so keen to have this on here, it’s absolutely critical to research to have good specimens that are well prepared.
“Hundreds of thousands of Tyrrell Museum visitors look in the Preparation Lab window each year…”
Wow. That’s the kind of impact you can have, working on dinosaurs in a densely populated continent.
In Mount Isa, far north-west Queensland, we’ve been getting about 6 to 7 thousand a year through the Riversleigh Fossil Centre. Without extra funding, that turns out not to be enough; the lab closes in a couple of weeks. 😦