Date: Wed, 15 Mar 2006 11:02:02 -0500
From: arne <arne
To: Shawn Dvorak <sdvorak
References: <002f01c647c5$87b0d400$0200a8c0
	<441838A0.1010900

Shawn Dvorak wrote:
> There was a recent thread on this, I think on this mail list, and also 
> apparently some discussion at the last AAVSO meeting.  Basically, one of 
> the glass layers in the filter composite is affected by moisture and 
> develops a tough, thin film.  It's easiest to detect the film by looking 
> even before the film is visible when just looking at the filter.  The 
> is the best approach.  I don't know if anyone has done any analysis to 
> see if there's any substantial color shift as the glass deteriorates.
> 
Gary Walker has found that applying hydrogen peroxide to the layer
dissolves it nicely without having to polish.  We haven't figured
out quite why yet, but I'd try that first.
Arne
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