Tissue compression can be the result of several things, 

Poor paraffin infiltration is one that can give problems

Poor knife angle

Tight adjustment on knife

Some blades have different bevel angles, also different coatings.

Accuedge from Sakura Finetek, Duraedge, Leica, Shandon, all are excellent
blades.

As for dulling a blade, it is a dangerous practice, and I have never met a
blade yet that is too sharp!  Better to use a paraffin block, empty, no
tissue, to work on edge.  
Duraedge says no this practice.



At 11:41 AM 1/10/01 -0500, you wrote:
>
>Hi everybody,
>
>I am looking for peoples opinions on the evils of tissue compression during
>routine parrafin sectioning.
>
>Our lab uses Curtin Matheson Scientific blades which produce clean sections
>(when new) but we experience serious compression when cutting some tissues -
>Most notably lipomas and endometrial curretage - of up to 25%.
>
>I have tried adjusting the angle, the temperature of the block,
>faster/slower cutting etc to no effect.  The archives talk about using
>different wax for infiltrating and embedding, but little about the day to
>day battle of cutting. (Incidentaly,we use the same wax for infiltrating and
>embedding.)
>
>Interestingly, using Leica blades produces almost compression-free sections,
>but bloody specimens in particular -emc or ecc for example- are unbelivably
>fragile and often croak before you can lay them out on the waterbath.  I
>like cutting with the leica because the  sections are SO good, if you have
>the time to be a little finicky.  Our contract of course is with CMS, so I
>jealously guard my dwindling supply.
>
>What do you guy's think? (Other than to fork out for Leica blades!)
>
>Tim Webster
>Northwestern Medical Center
>Fairfield Street, VT
>(802) 524-1070
>twebster@nmcinc.org
>
>
>
Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303