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Thread: HVLP viscosity cup

  1. #16
    Absolutely would love to see your viscosity chart. Thanks. Any idea where to find a Zahn cup online?

    The Fuji needle sizes are:
    #3 = 1mm
    #4 = 1.4mm
    #5 = 1.8mm
    #6 = 2.2mm

  2. #17
    Quote Originally Posted by Chris Stromberger
    Absolutely would love to see your viscosity chart. Thanks. Any idea where to find a Zahn cup online?

    The Fuji needle sizes are:
    #3 = 1mm
    #4 = 1.4mm
    #5 = 1.8mm
    #6 = 2.2mm
    Heres mine:
    #1 .75mm Inks dyes stains 16 seconds
    #2 1.00mm "all purpose", thin lacquers, water based finishes 16-18 seconds
    #3 1.5mm Catalyzed lacquers, conversion varnish (what ever that is) 18-24 seconds (I need the A or B air cap)
    #4 2.0 mm thined laytex paint, heavy primers 24-35 seconds (I need my B air cap)

    These are not a dead match but will sure give you a starting point. I'll search the net for a Zahn cup. You're getting closer. I really is a big help to get the viscosity right. When its right it goex on so well. When its wrong you have a frustrating mess. A Fugi is a good unit.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  3. #18
    Thanks for the info. I'll get some of the larger needles and try those with this oil pant.

  4. #19
    Quote Originally Posted by Chris Stromberger
    Thanks for the info. I'll get some of the larger needles and try those with this oil pant.
    I'd wait until you can measure the present viscosity. It may work with the 2.2 mm needle with a LITTLE thining.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  5. #20
    Join Date
    Mar 2006
    Location
    Round Rock, Texas
    Posts
    351

    Helped me also

    Byron: Following you discussion has helped me a lot. I never did get a reply from Porter Cable. Not surprised.

    I have 2 needles and caps:
    #1. 1.5mm for high solids, multipurpose.
    #2. 2.0mm for medium to high solids. Based on your chart, using a Zahn 2 cup I can get close to what I need for viscosity.

    Make sense?
    Mike
    Mike Hill

    Form Follows Function

  6. #21
    Join Date
    Mar 2006
    Location
    Round Rock, Texas
    Posts
    351

    Cup Prices

    I just did a search on line for Zahn Cups. The least expensive I found was $103.00! Now I am wondering why I did not buy a gun that had the cup included
    Mike Hill

    Form Follows Function

  7. #22
    I guess that explains why my gun came with its own "proprietary" viscosity cup, made of plastic. The Zahn ones I see online are made of stainless steel, come with a "cetificate of calibration" and are sold by scientific instrument places.

  8. #23

    Zahn Cup

    For those of you looking for a Zahn #2 cup, you can get one from Apollo. The contact is J. Danderand. $19.95 + shipping. Email them at jdanderand@hvlp.com

    Hope this helps.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  9. #24
    Join Date
    Mar 2006
    Location
    Round Rock, Texas
    Posts
    351

    Zahn Cup

    Byron: Thanks for the lead. I was able to get an aluminum Zahn #2 cup for $19.95 from Jason. A lot better than $103.00
    Mike
    Mike Hill

    Form Follows Function

  10. #25
    Join Date
    Dec 2013
    Location
    Bronx, NYC, NY
    Posts
    182
    Ah Ha! Another victim of the deviousness of paint manufacturers, or somebody.

    I'm in the throws of starting to spray coatings - in my case AquaZAR Interior Water-based Polyurethane, from UGL. The stuff is labeled as 55-60 KU.

    Now what is a KU? After an afternoon spent on the web, I find (on Wikipedia) that KU means Krebs Units, and is used solely with a Stormer Viscometer. This is industrial production testing equipment, and way out of our price range - I suppose, 'cause I haven't seen a price for the stuff.

    I haven't yet found a conversion table from KU to anything else, but a call to DuPont (the number on the can) got me talking to a gentleman who informed me that 60 KU is about 70 seconds using a Ford #4 cup. He found this out by looking up the viscosity of some substance (I don't remember what it was, if he even told me) in two tables, one in KU and the other in Ford.

    I bought a viscometer - after going to loads of paint stores. The one I finally got was a bit dusty, but it seems to work okay. It is a Dupont M-50, which corresponds to a Zahn #2, which, in turn, corresponds to a Ford #4.

    Of course this is only tangential to your question, but it is some sort of a start. What I think is that the maker of your spray equipment supplied a viscometer with no identification, and there are several different ones out there. The "number" for a Ford or Zahn or whatever relates to the diameter of the hole in the bottom. I've seen cups advertised with interchangeable tips - probably at interchangable prices: they'll give you a cup and tips and you'll give them your bank account.

    I did find a table containing the conversion equations for Zahn Cup #'s (#1 thru #5) to "Kinematic Viscosity in Centistokes". Here it is...

    ..Converting Cup Time (seconds) to Kinematic Viscosity in Centistokes
    Zahn Cup #1: V = 1.1(t - 29)
    => Zahn Cup #2: V = 3.5(t - 14) DuPont M-50, Ford #4 equivalent
    Zahn Cup #3: V = 11.7(t - 7.5)
    Zahn Cup #4: V = 14.8(t - 5)
    Zahn Cup #5: V = 23t

    I've used the Capital letter "V" instead of the Greek letter "nu" for the number in Centistokes.

    A "centistoke" is one one hundredth of a stoke.

    I don't know just how equivalent "equivalent" is.

    I have no intention of going into an explanation for Stokes vs Poise vs... If you are either interested or a masochist, go to Wikipedia and search for Viscosity.

    So far nothing for Ford cups.

    I think that what I'm going to do is simply thin the product, keeping track of how much thinner I put in it, until the product sprays okay. THEN - and only then - I will measure it's viscosity, record the number, and thin future purchases to the same number.

    The coating manufacturers seem to not give a damn about making their stuff easy to use, what with the various number systems in use, with no correlation. I fear that it is time for somebody - NIST, maybe? - to step in and require a standard, and that the manufacturers be required to list the number on the product containers, the spec sheets, etc.

    I mean - there are standards for most everything else we use: lumber, power, fasteners, tools, etc. Granted that many of the standards are voluntary, but the coating manufacturers have been around for a long time and still give us a mess.
    >>> Je Suis Charlie <<<

  11. #26
    I posted this link on the other thread. Hopefully it will relieve some of the stress:

    http://www.clearcoproducts.com/pdf/l...sion-Chart.pdf

  12. #27
    Join Date
    Feb 2003
    Location
    Doylestown, PA
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    7,551
    I mean - there are standards for most everything else we use: lumber, power, fasteners, tools, etc. Granted that many of the standards are voluntary, but the coating manufacturers have been around for a long time and still give us a mess.
    I suspect the reason there are no commonly available standard because spray finishing by consumers is a somewhat new phenomenon and a small % of a manufacturer's sales. Pro shops have 'internal knowledge' gained from experience or from manufacturers' reps and don't need published standards.
    Last edited by Curt Harms; 03-23-2015 at 7:56 AM.

  13. #28
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,645
    It's more practical to get a viscosity cup and use it to measure your incoming product, and then adjust it for your spray equipment, as required. A Ford #4 cup is typically used for many products that can be sprayed with an HVLP setup, and that's what I use. I measure the viscosity of every gallon of finish I get and write it on the lid. You'd be surprised how much the viscosity varies from one can to the next of the same product. From charts readily available on-line I know, for example, that a viscosity of around 45 seconds should spray well through a 1.8 mm orifice gravity feed HVLP conversion gun and it does with mine. So if I get a gallon of finish that measures 60 seconds I know that I'll need to thin it if I want to use that setup. From experience, I know that I'll probably have to add about 6% H2O for that product, so I'll add 4 or 5%, check the viscosity, and add more if required until I measure something close to 45 seconds.

    Even if the manufacturers listed the viscosity of their products on their PDS, and many do, you shouldn't expect the actual product you get to be exactly that number. At best, it's a guideline.

    John

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