[Histonet] Chicago Sky Blue stain vs. KOH - striking comparison

[John Kiernan]

The names Chicago blue and sky blue have been applied to various disazo dyes used in the past for direct dyeing of cotton. 
The name Chicago sky blue does not appear as a principal name or a synonym in either the 9th (1977) or the 10th (2002) editions of Conn's Biological Stains. In Conn9, there is a reference for staining fungi (Kuranz 1964) with ink blue, which was believed to be Chicago blue 6B (CI 24410, Direct blue 1).  This dye has also been used to quench autofluorescence prior to immunofluorescent staining, often as pontamine sky blue 6B or Niagara blue 6B. Closely related dyes are Chicago blue 4B (CI 24395, also called benzo sky blue 2B and brilliant benzo blue 6B) and benzo sky blue (CI 24400, Direct blue 15, also called sky blue and pure blue). 
 
Probably Chicago blue 6B (CI 24410, Direct blue 1) is the only one of these likely to be available. In the 1970s it was still an article of commerce with more than 70 brand names, but by 2002 it was no longer used industrially. The CI number and application name are the best identifiers, but remember that dyes often are mixtures and sometimes are mislabelled. None of these blue disazo dyes are certified by the Biological Stain Commission.
 
John Kiernan 
Anatomy & Cell Biology 
UWO, London, Canada. 
= = = 
On 10/11/11, "Harrison, Sandra C." <Sandra.Harrison3 <@t> va.gov> wrote:

> 
> Does anyone have ordering information for a stain called Chicago Sky
> Blue(CSB)?  I just saw an article in the NOV issue of ASCP LABMEDICINE
> (page 649) comparing KOH vs. CSB and, wow, is that a beautiful stain.  
> 
>  
> 
> The results were dramatic, with about a 25-50%  increase in the
> Dermatophytes identified and about a 5X increase in the Pityriasis
> versicolor identification.   
> 
>  
> 
> Thanks, 
> 
>  
> 
> Sandy C. Harrison, HTL (ASCP)
> 
> Histology Supervisor
>  
>