Embedding

Casting / Blocking

After infiltration, tissue is placed into a mold, and embedding medium solidifies to support sectioning

Ensure proper orientation of Tx for microtomy

Purpose of Embedding

Orientation

precise positioning of the tissue section inside the molder

Molding

provides shape to the tissue sample

Blocking

rapid solidification of tissue block

Casting

removal of tissue block from molder

Trimming

removal of excess paraffin wax from the mold

Leuckhart’s

Adjustable; allows for different block size

Two L-shaped heavy brass/metal strips on a flat metal plate.

Compound Embedding Unit

Series of interlocking plates resting on a flat metal base forming several compartments.

Plastic Embedding Rings and Base Molds

Consist of a special stainless steel base mold fitted with a plastic embedding ring

Peel-away

Gives perfect even blocking without trimming.

Plastic Ice Trays

Bended or pre-coated with glycerin/liquid paraffin to release blocks; practical for busy routine laboratories

Paper Boats

Economical and easy to prepare.

Ideal for celloidin and paraffin blocks

PLASTIC (RESIN) EMBEDDING

Provided superior results for light microscopic studies.

Used for sections thinner than 4-6 µm (e.g., renal and bone marrow biopsies), and undecalcified bone

Epoxy

Bisphenol A, Glycerol-based, Cyclohexene dioxide-based

Bisphenol A (Araldite)

Slow infiltration due to large molecular size.

Glycerol-based (Epon)

Lower viscosity.

Cyclohexene dioxide-based (Spurr)

Pure, lowest viscosity, fastest infiltration

Polyester

Introduced in the 1950s for electron microscopy, but now rarely used.

Acrylic

Made from esters of acrylic or methacrylic acid.

Used extensively for light microscopy.

Glycol Methacrylate (GMA)

Very hydrophilic

Methyl Methacrylate (MMA)

Ideal medium for uncalcified bones and other hard Tx

Double Embedding

A process where tissues are first embedded or fully infiltrated with a supporting medium, then infiltrated a second time and embedded in paraffin wax.