apochronaut wrote:Just wondering what you feel are the principle main difference is accounting for the quality variation between the Shandon microtome and the rocking microtome? Is it primarily the sharpness of the blades or is it a case of precision or other?
Hi apo' - a good question,
I would say the
main criterion is the
sharpness of the blade (availability of replacement blades notwithstanding). The Rocking Microtome in my opinion, and (considerable) experience of it's use, undoubtedly has the potential to cut 'good' sections through what I have found to be the optimum-range for botanical subjects, between about 5µ --> 12µ, maybe 15µ too.
It must be remembered that a significant factor limiting the quality of my sections, cut when the blade was new and at it's best, was that of
my own inexperience and lack of ability in using the Rocker to it's true potential.
When it performed well it did cut some good sections, it's very easy to use but cannot approach the accuracy of the Shandon - not even from a distance...
As an introductory instrument it is surely very good, but the inexperienced user will probably (I know I certainly did!) misuse it horribly and damage the blade very quickly indeed!
![Embarrassed :oops:](./images/smilies/icon_redface.gif)
Then the problem of sharpening blades becomes tangible - and it's a 'game-changer' - to get the blade sharp, at the exactly-correct angle and alignment, using all the necessary paraphernalia (and there's a lot) is for me and I would imagine many others, an unrealistic aim in the home environment with a 'normal' budget and a 'normal' amount of available time, not to mention the disinclination to perform this irksome task well.
The Rocking-Microtome's shortcomings can be avoided completely with regards to the blade by fitting a replaceable-blade system (holder) as found in the Shandon - universal replaceable blade holders are available for rotary microtomes but not for the Rocker however, and given that such a holder would cost in the region of twice the cost of the (rocking) microtome, probably never will, commercially at least!
Now, in terms of precision, quality etc, I would estimate the full potential of the Rocker to be able to deliver sections of
about 60% of the Shandon's best, quite a good performance considering just how good the Shandon has revealed itself to be in use...
The Shandon has of course the
precision, but whether a section has a 10% or a 50% margin of error is probably not a major factor for someone carrying out the sort of 'work' (It's a hobby after all, I'm a total amateur with a total amateur's needs) that I am.
Now the
retraction feature of the Shandon - this I consider to be a very large advantage indeed, the Shandon retracts the specimen-block by 40µ on each upstroke, eliminating the possibility of the block contacting the blade's back-edge during this return-stroke, the Shandon can cut up to 30µ thick and will therefore not go anywhere near (within approx 10µ at least) the blade with this feature in action. This really has a profound effect on the ability and tendency of a 'good ribbon' of sections being delivered from the blade. This ribbon-production is very important when 'moving through' a specimen to reveal related features as the depth into the specimen increases or approaches a region of interest therein.
The replaceable blade system is simply superb - a brand-new blade with a cutting-region of up to 80mm long approx whenever needed, for a cost as low as about £1.50 per blade for a 'std' blade (about £60 for 50 blades, delivered) up to about twice that - is very affordable indeed. To change a blade takes me about 30 seconds, enabling the routine use of one blade for 'roughing' and another for the fine-cutting of the sections to be used. Also the orientation of the blade remains completely consistent as the locking and carriage systems are extremely sturdy and stable when 'locked down' in use.
The Shandon is as a result of superb design and manufacture a
very easy instrument to use well, far easier than the Rocker. The Rocker also cuts sections through a necessarily curved path as the arm 'rocks' with a circular travel, albeit not very noticeable, it can be seen when the cut face of a block is examined and presumably therefore has the effect of giving sections that are thinner in the middle than at the start and finish edges of the wax-block.
Put briefly, the Shandon's advantages, and they are significant, are in my opinion due to the
blade's potential to always be at it's very best, combined with the sheer
quality and precision of it's construction & performance in all respects, not to mention the considerably superior
ease of use and resultant increase in
quality and consistency of sectioning.
With the use of steel blades requiring re-sharpening the Rocker soon becomes unusable and brings sectioning to a grinding halt - this is exactly what I experienced, leaving microtomy as an unattainable goal for the hobbyist without the £1,500 or more needed for the purchase of a used rotary, or perhaps about £700 for a copy of an old rotary design such as the old Reichert model first considered by myself...
I simply had an
amazing piece of luck when I acquired an
unused brand-new Shandon (complete with 10 replaceable Shandon blades!) for a
ridiculously low price (I actually paid £100 above the cost of a copied Rocking Microtome for it...).
This piece of luck has got me to where I am now but must surely be very,
very rare. My advice to you apo', is simple, if you can afford it, buy a rotary (used) such as the Shandon, that takes the simply superb replaceable blades. Ultimately I think a rocking microtome will become a heart-breaker...
p.s. I'm currently working (slowly) on a replaceable-blade holder that will fit into the rocker and take the same blades as used in the rotary microtomes, it's certainly working, the principle was demonstrated (see my earlier post re the use of a std razor-blade in my first trials) when I stuck a razor-blade to the rocker's ruined knife blade with sticky-tape, held my forefinger against it to keep the middle of it firm, and watched in amazement as the rocker produced several beautifully cleanly-cut sections where before I'd only managed tatty, ripped, holed and fragmented sections with the original knife!
This led me to the conclusion (correct thank goodness....) that the blade was the major factor ruining my sections, not the histological processing that was carried out on them. the rest is history, one amazing piece of luck later I'm up and running producing some great sections!
The reason I'm pursuing the replaceable system for the rocker is that I would
love to produce something that's cheap (and at this time It costs about
£3 to make one) to make and can be made by anyone, giving the rocking microtome back to folk that are starting out and can't afford a rotary microtome or expect the amazing luck that I've had...
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
That would make me very happy and I intend to keep working on this until I succeed with something that's demonstrably effective. No surrender with this one!
I hope this goes some way to answering your questions einman, these are of course only my own experiences and opinions, but are definitely based upon real-world experience. Good luck.
![Smile :)](./images/smilies/icon_e_smile.gif)