Embedding Blocks

Quick Answer: Embedding blocks are small, cube-shaped blocks to which a trimmed paraffin wax block containing a tissue specimen is attached, so it can be clamped in a microtome for cutting sections. They are used in histology and botany section-cutting practicals.

Where Embedding Blocks Fit in Histology

Before a soft tissue can be cut into slices a few micrometres thick, it has to be made firm. In the paraffin method, the fixed tissue is dehydrated through graded alcohols, cleared in a solvent such as xylene, soaked in molten paraffin wax and then set in a mould so that it ends up inside a solid wax block. That wax block is too small and too smooth to clamp directly in most microtomes, so it is fixed onto a holder first.

Traditionally the holder is a small hardwood or fibre block. The face of the embedding block and the base of the wax block are warmed with a heated spatula, pressed together and cooled, which welds them firmly. The block is then clamped in the microtome’s chuck, the wax face trimmed square, and sections cut and floated on warm water before being picked up on slides. In many modern labs, plastic embedding cassettes do the same job, forming part of the block during embedding.

The product photo shows small brown cube-shaped blocks with a ridged top face, which gives the molten wax something to grip. The material, dimensions and quantity supplied are not stated in the listing, and the block size should suit the clamp of the microtome in use.

Uses in Section Cutting

• Mounting paraffin blocks of animal tissues for cutting on a rotary microtome
• Preparing plant stem and root blocks for sectioning in botany practicals
• Teaching the full histology workflow from fixation to stained slide
• Keeping archived wax blocks attached to their holders, labelled for later sectioning

Specifications

Handling and Reuse

• Label each embedding block with the specimen code before attaching the wax, since blocks look identical once mounted.
• Scrape off old wax and wipe the block clean before reusing it for a new specimen.
• Store mounted blocks in a cool place so the wax does not soften and loosen from the holder.
• Keep the ridged face free of dust and grease, which weaken the wax bond.

Why Choose LabEquip

Histology and botany departments that cut their own sections need a steady supply of these holders for each new specimen. LabEquip lists them with its biology lab products; send the microtome model you use through the contact page so the block size can be checked against its clamp.

Frequently Asked Questions

What does embedding mean in histology?

Embedding surrounds a fixed, dehydrated tissue with a supporting material, usually paraffin wax, which fills the tissue and sets hard. The tissue can then be cut into very thin, even sections on a microtome without crumbling or compressing.

How is a wax block attached to an embedding block?

Warm a spatula over a flame, hold it between the base of the wax block and the face of the embedding block until both surfaces melt slightly, then withdraw it and press the two together. Add a little extra molten wax around the joint and let it cool fully before clamping.

Why must the wax face be trimmed square?

When the top and bottom edges of the block face are parallel, each section sticks to the one before it and forms a straight ribbon on the microtome. Uneven edges make ribbons curve or break, and loose sections are hard to handle.

What is the difference between embedding blocks and embedding cassettes?

The blocks are separate holders onto which a finished wax block is fixed. Plastic cassettes hold the tissue during processing and are pressed onto the wax as it sets in the mould, so they become the block holder automatically. Both end up clamped in the microtome.

Can embedding blocks be reused?

Yes. After sectioning, the remaining wax can be melted off or scraped away and the block cleaned for the next specimen. Discard blocks that have split or whose face no longer holds wax firmly.

Will the blocks fit my microtome?

Block holders must suit the clamp or chuck of the microtome. Many rotary microtomes clamp either cassettes or blocks of a set size, so check the clamp type and share it at enquiry so a compatible size can be supplied.

Last Updated: September 2026