Tarbosaur/Gigantoraptor - Macroelongatoolithus egg clutch cast

           This is the original Macroelongatoolithus egg clutch.  The original was valued at $14,000.00.  The first step is to prepare the specimen by filling in any gaps, cracks, or holes in the fossil specimen.  The purpose of this is twofold.  The obvious reason is to prevent the silicone from getting into places and then after the mold is removed you end up pulling pieces of the fossil off the specimen, thereby possibly ruining the fossil.  The second reason is that if the silicone gets into a crack, when the mold is pulled off, some of the siliccone remains in the crack and is nearly impossible to remove without tearing up the fossil to remove it.  Either way, you end up screwing up the fossil.  To prevent this potential damage we fill in any potential problem spaces with clay.  After the piece has been cast the clay must be removed to restore the specimen to its original condition.  The initial preparation of a piece, the casting process, and the clean up after usually takes about a week per cast.  This specimen had a HUGE amount of spaces to be filled.  In some places you could see daylight from one side of the eggshell to the other.  These pieces of eggshell would have obviously been torn off when the mold was removed and the mold would have been worthless as well with all the damage to the fossil.  For this reason we had to be very meticulous about our preparation of this piece (or any piece for that matter).  Even with all this preparation,  because the silicone adheres very tightly to the surface of the fossil some pieces may be pulled from the specimen when the mold is removed.  This is a consideration when selecting any specimen for casting.  We were very fortunate with this piece.  Only enough eggshell to equal the first joint on your thumb was pulled from the specimen and all but an amount equal to the size of your small finger nail was able to be restored to the fossil.

          As with most fossils, a considerable amount of matrix is still attached to the fossil.  Usually this is to protect the fossil from being broken.  For casting purposes this just creates too much mass to be reproduced economically and it detracts from the final cast.  It must therefore be excluded from the cast.  We usually do this by creating a hole to drop it into and them fill in around it to create a new artificial depth for the cast.  The next step in the casting process is to created a frame to contain the silicone while the mold is setting up.  We have begun to fill in dead  spaces within the frame, around the fossil, to reduce the amount of silicone required to produce a mold.  With silicone at nearly $1,000.00, wholesale, for a 5 gallon bucket you must do whatever you can to reduce expenses.  As it was, this mold took about one half of a bucket.  So, about $500.00 to make this mold.

          The third photograph shows the silicone being poured onto the fossil.  When you start pouring the silicone onto the fossil you must stay with it until you are finished pouring the mold.  The silicone itself is white.  The catalyst is dark blue.  When the two are mixed together you get this nice Robin's egg blue color.  The silicone is mixed up in batches of about 1200 grams at a time.  It gets a little trickier with batches of less than that amount, because you don't want to  mix up more than you need.  If you have more than you need, you can't save it and use it later.  The mixed silicone sets up completely within 24-48 hours depending on how much mass is involved.  You do have several hours which can be used for the molding process, but once the silicone is poured onto the fossil you don't want to be removing it from anything which it has touched.  This could create problems for producing a good cast.

          The last picture shows the original fossil at left and a painted cast at right.  





Original Macroelongatoolithus eggs

Eggs with mold frame

Silicone molding material being applied to eggs

Original clutch at left cast at right