70% ethanol is not considered a fixative.  Ethanol fixes by dehydration, so 
at a minimum you should be using 95% ethanol, and preferably absolute.  70% 
can be used as a preservative after fixation.  You have unfixed tissue if 
they are put into it immediately after harvest.  Since it is not a fixative, 
the length of time is not really a factor.  What is most likely happening is 
that you then dehydrate with higher concentrations of ethanol and the tissue 
is fixed at that time.  Ethanol alone is considered to be a very poor 
fixative, although it may be necessary depending on your application.  I 
suggest you either use a proper fixative such as a formalin variant, 
preferably overnight, or put your tissue directly into absolute ethanol for 
a few hours.

Bryan Llewellyn


----- Original Message ----- 
From: "Fawn Jones" 
To: 
Sent: Thursday, December 08, 2005 7:03 AM
Subject: [Histonet] fixation in 70% alcohol


>I just started working in a new lab and they use 70% Ethanol for fixation, 
>however I do not know how long to keep the tissues in 70% to ensure 
>adequate fixation. I am working with animal bones (mice, rats, sheep). 
>Could anyone give me suggestions on fixation times?
> Thank you
> Fawn Jones
>
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