Fabio,
I am sure that OptiVISOR is the trade mark. I believe it is made by Donegan Optcal Co. My set is X10 I bought it a long time ago and I believe it was aboaroundut $60. I have seen the fancier ones but I don't like "things" with too many gadgets; I still keep my childhood flare for breaking attachments to objects immediately, if not sooner.This set is very solid and I have traveled with it to many countries.
Emilio
----- Original Message -----
From: "Fabio Moretzsohn" <[log in to unmask]>
To: [log in to unmask]
Sent: Sunday, November 3, 2013 12:33:46 PM
Subject: Re: [CONCH-L] SS Mosquito Screen ?
Dear Emilio and all
Good test sieves in brass or stainless steel are expensive and a set can easily cost several hundred dollars; a single can cost more than $100. You can sometimes find used ones on eBay, or the new, odd-sized ones sold by people who don't know the price:
http://www.ebay.com/itm/Ele-International-Standard-Test-Sieve-1-25mm-Metric-1-0-Inches-Brass-/400271017306?pt=LH_DefaultDomain_0&hash=item5d3203055a
(this one has too large mesh size).
A cheaper alternative for collectors might be to make your own, as Emilio described, or "educational" test sieves with plastic frame and metal wire mesh (not brass or stainless steel), such as this set:
http://www.amazon.com/American-Educational-Screen-Sieves-Piece/dp/B006582JNC
I bought a similar set a couple of years ago; it is about 4-5 inches in diameter, with four mesh sizes; I've seen sets with 6 mesh sizes. I only use it with dry shell drift and it works fine, but you can only work with a small volume (I use about 1/2 a cup) at a time. The set is more portable than the more standard 8- or 12-in diameter sieves, and thus, easier to pack for a field trip. I have a few 8-in diameter brass sieves suitable for wet material.
Emilio, what model OptiVISOR do you have (or recommend)? I see that there are several models with lights, exchangeable lenses, and/or with a small loupe on one side. Again, one can find a wide range or similar products that vary in quality and price. I advise, from my own experience, to avoid products sold as "watch repair magnifier", such as this:
http://www.amazon.com/Magnifier-Loupe-Jeweler-Watch-Repair/dp/B00ARBTLWK/ref=sr_1_15?ie=UTF8&qid=1383502403&sr=8-15&keywords=watch+repair+magnifier
The inexpensive pair I bought (on eBay) works well for one eye, but it CANNOT work in stereo, i.e., there is no overlap of the field of vision from both eyes to see in 3D because of its poor design. Since I don't use, I guess I could try to bend the frame to achieve stereoscopic vision, but then the frame would not sit well on my face.
Cheers,
Fabio M.
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