Indicator on thumb screw indicates approximately 1mm diameter.

  1. Break carbon rod about 50mm - 75mm long.

  2. Insert flat end into the hole in the base of the carbon rod sharpener.

  3. Gently push the rod up into the cutter while rotating it in a clockwise direction. Hold the carbon rod sharpener so that any carbon dust falls into a waste container.

The formed tip should range from 0.4mm to 2mm in length to give the approximate film thickness shown in the table below.

It is often helpful to use a paper or porcelain indicator near the specimen. Approximate grey scale is indicated in the last column of the table.

IF:

M = mass evaporated
W = mass per unit area

W=

M

4o D2


D = distance to specimen

W= and t

t p

M


t = thickness (of carbon)
p = density (of carbon)

=V=

4o D2p or 2l


r = radius of carbon rod 
l = length of carbon rod
v = volume of carbon evaporated

M=

Vp and M = or 2 1p



t=

or 2.1 = r 2.1



4 or 2 1

Using the carbon rod sharpener as set, r = 0.5mm. For convenience, D = 100mm (with added block or platform) and the following table can be used directly.

1

t (approximate)

Indication

0.4mm

2.5nm

Very light

0.6mm

3.8nm

Light

0.8mm

5nm

Medium

1.0mm

6.2nm

Medium-dark

1.5mm

9.5nm

Dark

2.0mm

12.5nm

Very dark

(Refer to electron microscopy textbooks by Hall, Kay, Pease and others.)