Larry Legg's Learner Projects
|Hand-sectioning & Wax-embedding - Improving your Bench Microtome
It might be a good idea to read through Part 1 of this Project (if you haven't done so already) before continuing here. Part 1 gives a complete overview of this comprehensive hands-on project and you really need to have some background info before moving on to this and subsequent parts.
The Brunel Bench Microtome
This is an economically-priced microtome. It has several strengths and weaknesses. Much like you and me - nothing is perfect... and this microtome is no exception from this universal rule. Microscopy-UK decided to sell it in their online shop based on its considerable strengths, which - in their consideration - outweighed its weak points.
Let's look at its advantages first. The microtome is constructed of metal and is strong enough to last a considerable time. It is light enough to make it viable to ship around the world without having to take out a mortgage to pay the shipping costs. The chuck-size (where the wax block will be placed) is wide enough to accommodate quite large specimens... and not just tiny plant stems. Its unique feature is that it can be firmly clamped to a bench and therefore does not present the danger that a free-standing hand-microtome presents. Above all, its purchase price (even when shipping costs are added on, makes it an accessible and affordable item for every enthusiast throughout the world.
A lot of strengths but what about its disadvantages? Having purchased one... (no, my mate at MOL just isn't that generous to give me one for free), and used it, I found two things which need to be done to it for it to be a first class microtome. Now - I don't see the point in writing to Brunel or Mic-UK to get the microtome modified. Any modifications on a mass-produced item is likely to increase its price and we need to keep the cost of Microscopy tools low so that more of us can afford to practice the pursuit. The two modifications required are simple for us enthusiasts to do as you will see in a moment.
The microtome top plate is coated with something which inhibits a cutting tool from sliding across it smoothly. I think it is probably 'vulcanized. What happens is that a sharp edge can bite into the surface so that in time, you end up with a ragged surface which will keep snagging the cutting tool.
The center chuck which holds the wax block is not engineered fine enough to give a really snug fit into the central column: there is a slight amount of play in it. This will prevent you from obtaining a slice or section of consistent thickness because the block and chuck will move slightly during the cutting action.
The Microtome will still serve its purpose because these two weaknesses will not stop you obtaining sections per sec... but they will probably confound your attempts to get consistently perfect results every time. So let's fix it...
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