Rainbow Mountain Fossil Puzzle

Supplies

Half sheet of 1/2" marine grade birch plywood. Or other thin wood.

1" Dowel 10"

3/16 Dowel 1 1/2" Or chop stick

Wood Glue

Dozen 3/4" self tapping wood screws

Tools

Sabre saw

Screw driver

Bench Sander

Scroll saw

My two year old grand son had a love of puzzles. I wanted an accurate geology puzzle where the lower sediments in the mountain would be the older fossils you would find. To make it easy for a toddler I wanted it color coded. The color code would be the colors of refracted light with the longer wave lengths being the longer pieces of wood.

That was the premise and the hardest part. I went to his Great Grandpa Cal and we went through his geology books looking for fossil images that I could change into puzzles. I chose to use a trilobite, ammonite, plesiosaurus, tyrannosaurus, shark, insect, fish and rabbit to represent the time periods. The rabbit was to represent mammals and the top of the mountain was capped with white snow. White was also the color of all the lights before being refracted.

I started with a series of 9 sizes of circles I found around the house; a pizza dish, dinner plate, salad plate, bowl, saucer, etc. Each of the 9 circles was marked on a sheet of plywood and two sheets were screwed together with short screws. The screws were to hold the plywood together so I could cut 9 circles two layers thick. I cut them out with a sabre saw then smoothed the edges on a belt sander. After the twin circles were the same size they were separated. One side was to be the base for the puzzle and one the perimeter.

Using a copy machine I changed the size of the fossils to fit on the boards. The outline of the fossil was cut out. On the back side of the paper I drew three segments for each puzzle that would be easy to lock together. None of the parts were to be similar in shape so a toddler would not be easily confused. This paper cut out was attached in the center of the board with clear packing tape.

Using a scroll saw with a spiral blade cut the pieces out. The plastic packing tape melts and lubricates the blade. I can't take credit for that clever idea I read it in a book on puzzle making.Animal Puzzles for the Scroll Saw by Judy and Dave Peterson. I used a vacuum cleaner on blow to keep the dust away from the line I was cutting.

After the pieces were cut and sanded the perimeter of the fossils were glued to the backing boards. I was careful to not get glue in the center where the puzzle pieces would fit. The boards were all stacked from largest to smallest with the tops butted together.

An 1/8 inch pilot hole was drilled through each puzzle an inch and a half from the top edge. The bit only needed to be long enough to drill into the board below it to mark where the one inch holes would be drilled with a butterfly bit. To reduce splintering the butterfly bit was used on both sides of the boards such that the holes met in the middle.

A 1" dowel was rounded and a 3/16" hole drilled near the end. A 3/16" dowel was glued in the end like a T. This was to make it possible to transport and not have all the pieces separate. The final small disc was not a puzzle it was only to cover up the rabbit so no loose pieces would be exposed.

The painting was done with diluted acrylics as a wash to let the wood
grain show. The two white boards had to use non diluted paint as the white wash was not pretty. Both the edges and the back were stained at least three times. When dry the back sides of the puzzle pieces were sanded to make it obvious they were upside down if they did not have any stain. Every surface was then sprayed with clear spray to seal the wood.

The puzzle was a huge success and the fossils are fun to make frighting shadows with.