Re: [Histonet] Microwave slide drying vs. conventional slide drying

From:Rene J Buesa

Hi Lori:
  When you place slides with sections in the microwaves oven (MWO) you are not heating the paraffin, you are heating the slides.
  Paraffins are non polar molecules and do not vibrate under the microwaves (MW), they are "blind" to the paraffin that has a penetration ratio of 15,000 cm.
  MW go through the paraffin as if it did not exist at all. 
  That is not the case of water that has a penetration ratio of just 4.4 cm. This means that placing the slides in a MWO you will melt the paraffin but because the glass in the slides heats (and could break because glass, as you know, if a very bad heat conductor).
  For this reason some tissue processors that use MW (like the "newest" Sakura) has 3 chambers, the first 2 heated under the influence of MW and the last, where the
  paraffin rests, is heated electrically; the infiltration is due to the effect of pressure and vacuum.
  You should heat your slides either in a hot plate (has to be really big to accomodate a large number of slides) or in a conventional convection oven (I prefer this method).
  The Sakura stainer heats the slides at 70║C during just 7 minutes in a heating chamber before taking the slides to the first xylene.
  I hope this helps you to argue your case with your doctors.
  RenÚ J. wrote:
  We are having a discussion about slide drying at out facility. How many of you out there use a microwave to dry your H&E slides before staining versus using a conventional 70 degree Celsius hot air slide drying oven for 20 minutes? I personally against microwave slide drying but the doctors like it because it takes less time (3 min. 30 sec. on medium setting). Thanks for your response.

Lori A. Harris, HT (ASCP)
Histology Section Leader
GSRMC - Pathology
3600 NW Samaritan Drive
Corvallis, OR 97330

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