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Thread: HVLP viscosity cup

  1. #1

    HVLP viscosity cup

    Do any HVLP users out there use the viscosity cup? I have been experimenting with oil paints and some waterborne poly. The poly registered a fairly high viscosity with the cup that came with my Fuji, but I am able to successfully spray it without thinning (using a #4 tip). I'm wondering if I will always get better results adhering to the manual's viscosity numbers. Eg, for oil paint they say 20-25, I think (don't have the manual in front of me). The oil I am using is off the charts viscous out of the can. I am thinning to the paint mfgr recommendation, and it still is showing a high viscosity number wit the cup (like 70 or so if I recall). Just wondering if those viscosity numbers are hard rules--do people here follow them as listed in the book? Do you generally ignore the mfgr thinning recommendation when spraying with HVLP and thin to the "official" recommended viscosity?

    Thanks,
    Chris

  2. #2
    Chris,
    I use an Apollo system and have the Zahn #2 cup. Until I adhered to the viscosity numbers, ie thinning, I had all kinds of trouble. I learned about the importance during one of those mini-seminars at your yearly wood working shows. I went home, tested the material and found that that after 10% thinning, the material atomized beautifully. Now I don't spray squat until I test the material.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  3. #3
    Join Date
    Feb 2003
    Location
    Conway, Arkansas
    Posts
    13,181
    Quote Originally Posted by Byron Trantham
    Chris,
    I use an Apollo system and have the Zahn #2 cup. Until I adhered to the viscosity numbers, ie thinning, I had all kinds of trouble. I learned about the importance during one of those mini-seminars at your yearly wood working shows. I went home, tested the material and found that that after 10% thinning, the material atomized beautifully. Now I don't spray squat until I test the material.
    Oh man....Excellent advice and right on the money too!!!
    Thanks & Happy Wood Chips,
    Dennis -
    Get the Benefits of Being an SMC Contributor..!
    ....DEBT is nothing more than yesterday's spending taken from tomorrow's income.

  4. #4
    Join Date
    Mar 2006
    Location
    Round Rock, Texas
    Posts
    351

    Finding Viscosity

    I have been using some Sherman Williams NS Lacquer and am trying to determine what it's viscosity should be for spraying. The instructions say it does not need thinning, but 10% thinner can be added. I printed a data sheet for the product from their web site, but no viscosity number. So I am left with trial and error. Any recommendations on where to find this number?
    Mike
    Mike Hill

    Form Follows Function

  5. #5
    Not sure. I have noticed on some product's MSDS (data sheet) there is a viscosity number in units of "KU" I think, but not sure if you can translate that into "viscosity cup units". I just go by the sprayer's recommendation. Mine came with a viscosity cup and most things seem to require 20-25 on their cup, according to the sprayer manual. So I have been thinning until I reach that viscosity.

  6. #6
    Quote Originally Posted by Mike Hill
    I have been using some Sherman Williams NS Lacquer and am trying to determine what it's viscosity should be for spraying. The instructions say it does not need thinning, but 10% thinner can be added. I printed a data sheet for the product from their web site, but no viscosity number. So I am left with trial and error. Any recommendations on where to find this number?
    Mike
    Mike,
    Your gun instructions should tell what viscosity is required for the various needles they supply. Further they shold tell what viscosity scale they are referring to. Mine is a Zahn #2. I have a Zahn cup (came with gun). You fill it and time how long it takes to empty. That time then tells you which neddle to use. If the time is longer than the needles you have, you have to thin it until the time is correct. With the proper viscosity, the material should spray very well. If its too thick it will splatter comming out; too thin it will run like crazy. You can PM me if you wish and we can get into details.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  7. #7
    I was sitting here re-reading this thread and decided to try and consolidate the viscosity information into a form that makes sense (I hope).

    First, viscosity is its simplest terms, is how thick/thin the material is based on some standard and is measured in time. If a paint manufacturer states the viscosity without stating the method used the number is useless. I use Zahn #2 because that is what came with my gun. there are other way to measure viscosity but the procedure is the same.

    Second, you need to know what you gun manufacturer uses as a standard, Zahn or what ever, to measure viscosity. Again, mine uses Zahn #2. Your gun should come with more than one needle/nozzle set. If not, you may have to buy additional sets to accommodate various thicknesses (viscosity) of paint.

    Third, your gun manual should have a chart that states the viscosity (time) for each needle set. Mine came with four needles, #1 - #4. #1 is for dyes and some stains and the time to empty my Zahn #2 cup is 10-15 seconds. Needle #2 takes 15-18 seconds; #3 18-23 seconds and #4 25-30 seconds.

    Fifth, fill cup and measure how long it takes to empty. Take that time and look at your chart and match the needle/nozzle set that most closely matches the time. If your time is longer than any needle/nozzle set you have you can either thin the material OR buy a bigger set. I do not recommend that you thin material more than 10-12%. Beyond that and you start degrading the paint.

    If you are like most of us, you will tend to keep using the same material to finish your projects so once you know which needle to use you won't have to do it the next time. If you buy something you haven't used in the past measure the viscosity. I don't trust any numbers on paint cans!

    I think the best advice I can give you is to get very familiar with your guns characteristics. If you think you need more needles/nozzles, contact your manufacturer for the parts. Also, if it is not clear what system they use to measure viscosity, again contact them and find out. Also, make sure you have the equipment to measure the viscosity.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  8. #8
    Quote Originally Posted by Byron Trantham
    Third, your gun manual should have a chart that states the viscosity (time) for each needle set.
    My gun (Fuji MM4) only mentions one set of viscosity numbers, different according to material. Eg, "primers 30-40", etc. No indication of numbers correlated to tip sizes. Also, I don't think it mentions what kind of viscosity cup it came with (Zahn or Ford etc).

    Quote Originally Posted by Byron Trantham
    I do not recommend that you thin material more than 10-12%. Beyond that and you start degrading the paint.
    This is the part that worries me. I'm spraying oil based enamel paint, and I have to thin the heck out of it to get it down to the proper viscosity. I'm dealing with loss of sheen in the satin enamel due to the amount of thinner I have to add.

  9. #9
    Quote Originally Posted by Chris Stromberger
    My gun (Fuji MM4) only mentions one set of viscosity numbers, different according to material. Eg, "primers 30-40", etc. No indication of numbers correlated to tip sizes. Also, I don't think it mentions what kind of viscosity cup it came with (Zahn or Ford etc).

    This is the part that worries me. I'm spraying oil based enamel paint, and I have to thin the heck out of it to get it down to the proper viscosity. I'm dealing with loss of sheen in the satin enamel due to the amount of thinner I have to add.
    Absolutely contact Fuji. I am sure the numbers you have are for the needle/nozzle provided. Find out if they have larger needles and a Ford/Zahn cup to measure the viscosity recommended for the needles they do offer. You're on top of this, you just don't seem to have the correct needle for the paint you are trying to spray. Thinning is last resort but can certainly be necessary. Are you using a turbine? If so, how many stages?
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  10. #10
    I will contact them to get more details. It's a 4-stage turbine system. I'll post here if I get anything interesting from them.

  11. #11
    Quote Originally Posted by Chris Stromberger
    I will contact them to get more details. It's a 4-stage turbine system. I'll post here if I get anything interesting from them.
    Chris, a four stage unit should allow you spray just about anything including latex but you need different needles for different materials. I'm using a regular air compressor and a conversion gun. I works fine but the compressor runs it's ... off. Next month our yearly wood show happens and I am pretty sure the "biggie" this year is going to be a four stage Apollo.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  12. #12
    Got a reply from Fuji. The viscosity cup that comes with their system is not any of the standard varieties, it's just their version I guess.

    And re the different viscosity numbers for different air cap sizes, this was the reply: "Each aircap size does not need a different set of viscosity numbers - it's the paint viscosity that determines the amount of thinning necessary and the viscosity numbers"

    Now I'm even more confused!

  13. #13
    Quote Originally Posted by Chris Stromberger
    Got a reply from Fuji. The viscosity cup that comes with their system is not any of the standard varieties, it's just their version I guess.

    And re the different viscosity numbers for different air cap sizes, this was the reply: "Each aircap size does not need a different set of viscosity numbers - it's the paint viscosity that determines the amount of thinning necessary and the viscosity numbers"

    Now I'm even more confused!
    Chris, I am sorry to hear their answer. I doesn't make sense. Most paint does not come with viscosity numbers and if they do, its related to one of the standards like Zahn or ford. The air cap does not control how much paint is sprayed only the fan pattern. The needle hole controls how much is sprayed (with the same air pressure). My set does come with one other air cap and it is used with my largest needle #4. I don't have any advice here. I hope you can work it out.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  14. #14
    Hmmm, ok. Their "air caps" come with needles also. I guess they change the cap a bit for each needle size too. Well, thanks for the help. I'll keep experimenting!

  15. #15
    Quote Originally Posted by Chris Stromberger
    Hmmm, ok. Their "air caps" come with needles also. I guess they change the cap a bit for each needle size too. Well, thanks for the help. I'll keep experimenting!
    Hey, that's good news because there is a relationship between the needle/air cap size and viscosity. You can buy a Zahn #2 cup. There should be a chart out on the net somewhere that relates needle diameter and viscosity. Heck, if you want I can measure mine in thousands and provide the recommended viscosity for each needle diameter from my chart. Buy yourself a Zahn cup and keep track to see what times are best for your needles. Let me know if you want my information as a starting point.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

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