If you want to look at microfossils in any sample, a picking tray is absolutely essential. These allow the prepared residue to be thinly spread for easy examination under the binocular microscope. Don't be tempted to put too much material on the tray - it is always better to have a thin layer or you will miss a lot. These usually have a gridsquare pattern on them so you can pick systematically moving slowly down each grid. The sides of the tray should not be either too low or too high
Metal picking trays are the best but these can be expensive. Expect to pay between £10-15 (2003 prices).
This guide, the second in the series, will give step by step instructions on how to make a much cheaper but extremely usable substitute.
- A 9cm wide and 12 cm long rectangle thick black card.
- Two seven cm long x 0.7 -1 cm wide strips thick black card.
- Two 11 cm long x 0.7 -1 cm wide strips thick black card.
- A stanley knife/craft knife and a cutting board to cut the pieces (please note - it is impossible to pick microfossils without any fingers so care should be taken at this stage!).
- A ruler and sharp pencil or fine tipped white/silver ink pen.
- Glue or staples. Glue is best as with staples you will scratch the base of your microscope.
Dimensions can be adjusted to suit. One of the benefits of making your own - the bought trays only come in one size.
1) First take your rectangle of card and fit the cut strips along its edge. Mark their position and put aside for the time being.
2) Then draw an evenly spaced gridsquare about 10cm long by 6 cm wide in the centre of the rectangle using a ruler and a pencil or very fine tipped white/silver ink pen. You might find that numbering the squares helps you to work through the tray systematically - I have done this on both my home made and bought metal tray.
3) Glue or staple the card strips in place along the edge. For a slightly higher edged tray use two strips (check first before glueing/stapling.
4) Allow to dry
That is it!
The best brush for picking is a very fine 00 grade artists sable brush - not cheap but they last for a few years before completely wearing out and becoming unusable. Synthetic examples are cheaper but are less durable.
I hope this has been of some interest. Photographs of both the card and metal picking trays are available by email on request.
UPDATE: July 2009: I will be adding a photograph shortly