DURING SECTION CUTTING

Question 1

Sections fail to form ribbons

Answer 1

REASONS:

Surfaces and edges of the block are not
parallel
Horizontal surface of the block is not
parallel to the knife
Paraffin wax is too hard
Knife is tilted too much
Sections are too thick
Knife is dull

Question 2

REASONS:

1.Surfaces and edges of the block are not
parallel
2. Horizontal surface of the block is not
parallel to the knife
3. Paraffin wax is too hard
4. Knife is tilted too much
5. Sections are too thick
6. Knife is dull

Answer 2

REMEDY
1.Re–trim the block
2. Re-adjust and re–orient
3. Coat the horizontal edges of the block with wax of a lower melting point
4. Reduce the tilt
5. Readjust the thickness of the sections
6. Hone and strop

Question 3

Sections roll up on cutting so
that they adhere and get
broken against the knife edge

Answer 3

REASONS AND REMEDY

Knife is blunt- Sharpen the knife
Tilt of knife is too great- Reduce the tilt
Knife edge is dirty- Clean the knife edge

Question 4

Ribbon is curved, crooked or
uneven instead of straight

Answer 4

REASON:
Blunt or dull spot on the knife
producing an irregular knife edge

REMEDY:
Adjust the knife so that knife edge will present a uniformly sharp edge to the block; or sharpen

Question 5

Ribbon is curved, crooked or
uneven instead of straight

Answer 5

REASON:
Edges of the block are not parallel but
round or wedge shaped

REMEDY:
Re–trim the block

Question 6

Ribbon is curved, crooked or
uneven instead of straight

Answer 6

REASON:
Knife is not parallel to the block

REMEDY:
Readjust the knife and the block

Question 7

Ribbon is curved, crooked or
uneven instead of straight

Answer 7

REASON:
Paraffin is impure

REMEDY:
Repeat impregnation using pure wax

Question 8

Sections are compressed,
wrinkled or jammed

Answer 8

REASON:
Knife is blunt or dull

REMEDY:
Re–sharpen the knife

Question 9

Sections are compressed,
wrinkled or jammed

Answer 9

REASON:
Paraffin block is warm and soft

REMEDY:
Cool the block on ice water until firm

Question 10

Sections are compressed,
wrinkled or jammed

Answer 10

REASON:
Knife edge is coated with paraffin

REMEDY:
Clean the knife edge

Question 11

Sections are compressed,
wrinkled or jammed

Answer 11

REASON:
Sections are too thin

REMEDY:
Readjust thickness of section

Question 12

Sections are compressed,
wrinkled or jammed

Answer 12

REASON:
Microtome set screw is loose

REMEDY:
Tighten the screw

Question 13

Sections are compressed,
wrinkled or jammed

Answer 13

REASON:
Tilt of knife is too vertical

REASON:
Reduce the tilt

Question 14

Sections are torn and
crumble when cut

Answer 14

Incomplete dehydration, clearing,
and/or infiltration tissue with wax- Remove paraffin with clearing of agent, pass thru decreasing grade of alcohol, then repeat dehydration, clearing and embedding

Paraffin is warm and soft- Cool and harden paraffin in ice for ¼ to ½ hour

Knife is blunt -Sharpen the knife

Question 15

Sections are squashed
(the width of each section
less than that of block)

Answer 15

REASON:
Bevel of knife is lost due to incorrect
sharpening

REMEDY:
Re–sharpen, using a knife back or automatic knife sharpener

Question 16

A hole is formed in the
section

Answer 16

REASON:
Bubble or dirt formed in the embedding medium

REMEDY:
Re–embed in freshly filtered wax if necessary

REASON:
Hard spot in tissue possibly due to
calcium

REMEDY:
Once embedded in paraffin wax, decalcification is impractical; use
base–sledge microtome with a wedge knife

Question 17

Selections of unequal
thickness are produced

Answer 17

RS: Tilt of the knife is too great or bevel is
not cleared, hence object is
compressed against the knife’s edge
REMEDY: Reduce the tilt.

RS: Clamp set screw on knife or
blockholder is loose
REM: Tighten screw

RS: Blocks are too large
REM: Cut blocks into smaller fragments

RS: Blocks are too hard
REM: Soften blocks in detergent or phenol

Question 18

Sections adhere to the knife
or other parts of the
machine

Answer 18

REAS: Static electricity due to low
atmospheric humidity
REM: Breath out or blow gently on the block and knife to break up static electricity or boil water in the room to increase the humidity

RS: Knife edge is dirty
REM: Clean the knife edge

RS: Knife edge is dull
REM: Sharpen the knife

RES: Knife edge is too great
REM: Reduce the tilt

Question 19

Ribbon is split or lengthwise
vertical scratches are seen on
sections

Answer 19

RS: Nicks are damage on the knife edge
REM: Sharpen the knife

RS: Dirty embedding medium
REM: Re–embed in filtered wax

RS: Knife edge is dirty
REM: Clean knife edge with xylene

RS: Tilt of knife is too great
REM: Reduce tilt

Question 20

Resistance is felt on the
lower part of the section
during cutting

Answer 20

RS: Tilt of knife is insufficient; paraffin block
is therefore compressed against the
base of the knife towards the end of
stroke

REM: Increase the tilt

Question 21

Horizontal or parallel lines or
furrows across the section
(chatters) are seen, forming
thin and thick zones

Answer 21

REASONS
Knife edge vibrates due to:
(a) hardness of the tissue
(b) tilt of the knife is too great

REMEDY
Treat with phenol during processing; or colloidionize
Reduce the tilt

Question 22

Section cut is sometimes
thin, sometimes thick

Answer 22

RS: Knife is blunt
REM: Sharpen knife

RS: Knife is not clamped properly
REM: Adjust the knife

RS: Tilt of knife is too great
REM: Reduce the tilt

RS: Knife or blockholder is loose
REM: Tighten adjusting and locking screw

RS: Knife tilt is too small that block is
compressed by bevel and section is not
cut
REM: Increase the tilt

Question 23

Knife makes a hard metallic
scraping or ringing sound on
backstroke, when section is
cut

Answer 23

RS: Tilt of knife is too slanted or too big
REM: Readjust the angulation of the knife

RS: Tissue is too hard
REM: Take fresh block treated with phenol during processing

RS: Knife blade is too thin
REM: Charge the knife

Question 24

Frozen tissue crumbles and
comes off the blockholder
when cut

Answer 24

RS: Freezing not adequate

REM: Refreeze the tissue block

Question 25

Frozen tissue chips into
fragments when cut

Answer 25

RS:Tissue is frozen too hard

REM: Warm the tissue with the fingers