Ian,
I was thinking the same way as Gayle did. But apparently this wasn't the problem. I wondered what AP chromogen you are using? I have very good results using the newest Dako Liquid Permanent Red substrate kit.
The KPL universal blocker Gayle suggested I don't know. However, I am familiar with a similar Dako product called Dual Endogenous Enzyme Block. This blocker also applied before the IHC procedure also effectively destroyed some of my epitopes resulting in a bit too clean staining result indeed.... So be careful with this stuff.  
Furthermore, I am using PowerVision-AP with great results.
Hope this helps.

Chris van der Loos, PhD
Dept. of Pathology
Academical Medical Center
Meibergdreef 9
NL-1105 AZ Amsterdam 
The Netherlands
phone: +31 20 5665631  

----- Original Message ----- 
>From  Ian Montgomery  
Date  Thu, 18 Nov 2004 17:22:06 +0000 
To  histonet@lists.utsouthwestern.edu 
Subject  Fwd: Re: [Histonet] Envision. 

>
>Question:  what buffer are you using?   If you use PBS, then you will have 
>phosphate ions available for AP, TRIS buffered saline is preferred with AP 
>protocols.
Gayle,
         I'm using TBS as suggested by Dako. With and without Tween, but 
still the same result.



>At 08:52 AM 11/18/2004, you wrote:
>>         I wonder if anyone can offer any hints and tips for Dako 
>> Envision. Localisation is fine, HRP is clean but alkaline phosphatase, 
>> despite my efforts, is still giving me quite a lot of background. This 
>> manifests itself as a fine red ppt. over the specimen.
>>Ian.
>>
>>Dr. Ian Montgomery,
>>Histotechnology,
>>Graham Kerr Building,
>>Institute of Biomedical & Life Sciences,
>>University of Glasgow,
>>Glasgow,


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