You have pretty much covered all the possible problems, so it is difficult to have an idea about the causes of the problem.
If I understood you well those blocks cut OK in your friend's labs, but not in yours? Then what is that you do differently while sectioning that is not done in your friend's lab? That would be a start.
Regardless of wht you think this seems to be an infiltration problem or a poor adherence between the paraffin used in the last bath and the one used in the embedding center. Even if you put the blocks in melted paraffn x2 hours, how was the last paraffin in the tissue processor?.
Do you have to take serial sections? Can you just take one section at a time leaving them less time in the water bath?
Again, this is typical behaviour when the tissue is not well infiltrated.
Try a cold water bath and add liquid detergent to it (0.20-0.25 mL) to allow the sections to expand even at low temperature, perhaps you will be able to prevent the paraffin to separate from the tissue.
Carl Hobbs wrote:
A colleague has brought his pwax blocks of brain tissue from his lab and is
using my pwax section cutting system to cut his blocks: after floating them
out on the waterbath ( fresh distilled water, maintained at 40C- yes, we've
tried lower temps and the sections either just don't flatten out or still
separate, after a longer period), they separate away from the wax, initially
along the line of the meninges separating the two areas of brain, in coronal
I have looked at his blocks and they seem well-processed - no
fracturing/white areas, a good way to tell is to look at the cut blocks a
week after sectioning to see if the face of the tissue has shrunk down into
the block, no they haven't.
I have cut some myself: same problem.
I took one of these blocks and re-immersed it in fresh molten wax for 2hrs
( I tried simple paraffin wax and then Paraplast Plus)....no improvement.
The blocks serial-section beautifully.
He has asked his lab if they have this problem and they do not. He has not
seen it before, either, when cutting in his own lab.
This happens to me also, with the occassional block. Has anyone come across
Why does it occur?
( my processing details: 2hrs in each of 30, 70, 95, 100, 100% IMS,
IMS:Xylene 1:1, xylene, xylene, wax, wax...then 1hr in embedding station wax
bath. On a Leica processing machine, with agitation.
Embedding is swiftly carried out, so minimal cooling of wax.
Be most grateful for any reasoning.
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