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-   -   Paint Viscosity Follow Up (http://www.hotrodders.com/forum/paint-viscosity-follow-up-75111.html)

x711 11-30-2005 08:48 PM

Paint Viscosity Follow Up
 
In a previous post I had asked about the right Viscosity that paint should
be in order for it to spray correctly, Anyway I had some good responses
from people that were interested in the Thread and wanted to follow up
with some results that I had obtained.

My basic question was to try find a method of checking the viscosity
of the paint, Milo I believe mentioned using a Zahn 2 Cup. Well today
I got one for a real good deal so I could not resist the purchase
"Got to have our toys" :) lol

Anyway, Some interesting results. I purchased some good Quality single stage
paint from a local supplier and they said they mixed it so that it was ready
to spray "RTS" All I had to do was add the hardener. Anyway the results
of my painting have been pretty ok but I felt that the material was a little
thick or something was wrong with the way it layed down.

On the Data Sheet the viscosity of the material "RTS" according to Valspar shold be in the range of 20 - 22 seconds measured with #2 Zahn cup.

I measured my paint which looked ok to me but found that it gave me a
reading of 55 seconds and thats without the Activator added, Eh something
aint right with this picture. "So the paint is too thick" Come to find out that
the paint really needs to have the consistency that is slightly thicker than
water so that it will spray correctly.

I wanted to post this info as a newbie might run into the same problems as
I did.

FYI: Measuring standard tap water on a No 2 Zahn cup returns 15 seconds
or so. So if the data sheet for your paint states a particular viscosity you
now should have an idea of what it should look like in advance !

comments welcome.

Thanks guys. X

milo 11-30-2005 09:05 PM

When I first started out , like you I really wanted to get it just right and used the Zahn cup with a stopwatch also. Then it became a issue cleaning the thing after each batch but that was the price of following the learning curve.

After a while once the mix is how you like then you can touch a sample from your mixing stick to a nearby vertical suface and learn the rate a sample runs down after it leaves the paint stick. Soon you'll be able to recognise perfect viscosity weather it's primer or paint or clear ...

Good to see you having fun with it too... helping others is the best way to help ourselves :welcome:

x711 11-30-2005 09:38 PM

Hey thanks Milo,

When I get it down a bit better, Im gonna try your stick method.

Having fun at this end and making progress, wow light at the
end of the tunnel !

Thanks X

jcclark 12-01-2005 07:13 AM

I was very interested in what you were asking because I paint with other
products beside car paint and most of them have no thinning instructions
for spraying. Like wood polyurethane, meant to be put on with a brush
but some spray it so how much do you thin?
everyone I've asked gives me a different answer.
Somewhere, someplace there's bound to be a chart or something
stateing what viscosity matches what tip size.
I would love to see that.

x711 12-01-2005 08:15 AM

Hi Jim, Yeagh im interested in this stuff alot too as you can see :)

For a chart of Viscosity for the guns I think your best bet would be to contact the manufacturer of the gun. I believe since the gun manfacturers are in the business of making guns then they also got to be in the business of knowing what the "Eflux" or viscosity of the liquid that a certain tip size or cap size can spray. They have to have this data otherwise what could they base a gun creation on.

I will do some hunting around on this a bit more to see if I can gather additional data.

Its kind of a inportant issue when you think about it. So the more we know
the more productive we can be right from the get go.

Thanks. X

MARTINSR 12-01-2005 11:13 AM

Hold on here X, you measured your viscosity without mixing it? I re-read your post a few times and still see the same thing, you only checked the PAINT, that viscosity recommended by the manufacturer is mixed and ready to spray, so your results mean nothing, not one single thing.

I have never seen the term RTS on anything other than a 1K product that was LITERALLY ready to spray out of the can. By definition "RTS" means there is NOTHING to be added. So if Valspar is calling a product that needs a hardener "RTS" they are going to confuse a lot of people. There are plenty of products from IMRON to clears that are "prereduced" and you only add the hardener in a let's say 4:1 mixture. Are they saying these products are "RTS"?? NO OTHER manufacturer calls a product that you add a hardener to RTS, does it actually say that on the can or literature?



Brian

x711 12-01-2005 12:10 PM

Hi Brian, I measured the Viscosity of the paint I had received in the can.
It was way above what the data sheet said for a "RTS" viscosity without
mixing in the Activator. Adding the Activator will and did make the paint thicker.

My point from the earlier post was that while the paint looked ok from
a visual perspective, the stuff measured with the Zahn 2 cup produced
results that were way out of spec with what the spec sheet states for a
"RTS" Viscosity. Prior to runing the test, I made sure the paint in the can
was mixed with a stick.

My measurements are valid. Are you seeing where im coming from now ?


Page 2 of the data sheet says.

AIR PRESSURES
Conventional @ Gun PANEL OVERALL
Gravity Feed. . . . . . . . . . . . . . . . . . . . . . 30-35 psi. . . . . . . . 35-45 psi
Siphon Feed . . . . . . . . . . . . . . . . . . . . . . 35-45 psi. . . . . . . . 45-55 psi
HVLP @ Cap . . . . . . . . . . . . . . . . . . . . . 8-10 psi. . . . . . . . 8-10 psi

PHYSICAL DATA
VOC (Ready-to-Spray) . . . . . . . . . . . . . . Coating: 3.5 lbs/gal (Max)
Volume Solids . . . . . . . . . . . . . . . . . . . . 47.4% (Avg)
Theoretical Coverage . . . . . . . . . . . . . . . 760 sq. ft. per mil per gallon (Avg)
Recommended DFT . . . . . . . . . . . . . . . . 1 - 3 mils.
Zahn #2 Viscosity (RTS) . . . . . . . . . . . . 20 - 22 seconds

"I assume the Zahn 2 Viscosity would include the Activator"

Here is a link to the actual spec sheet, check it out.

http://www.autopaintdirect.com/data/840.pdf

Thanks.... X

x711 12-01-2005 12:13 PM

Jim I found a good link that might give you some insight on the tip size to use
vs Viscosity of material you wish to spray.

Here you go.

http://www.spraygunindustry.com/Info...nViscosity.htm

Interesting stuff.

Thanks X

jcclark 12-01-2005 01:15 PM

Thanks Mr. X. Just what I wanted to see.

MARTINSR 12-01-2005 01:23 PM

What is the temp of the paint and hardener (is it room temp?) and what was the Zahn cup reading with the hardner added?

Brian

x711 12-01-2005 06:58 PM

Brian, when I checked the paint last night the temp was about 57 degrees F
the activator added right about 8 seconds to that time. If you look on the data sheet page 1 they offer various activators, from the top down they get
thicker in viscosity. I was using the warp speed one. I have others and they
are less viscous. The warp speed one looks like treacle but is clear in color.

Today I left the paint in a warmer room that was right around 72 degrees
for more than 8 hours. Measuring the paint just awhile ago produced a Zahn 2
reading of 35 seconds. Thats a 20 second difference just on the paint.

I will be spraying right around 65 F later this week so my intent is to mix the
paint knowing its temperature and reduce as needed to bring it into the
correct window as indicated on the data sheet.

I might just try use a medium reducer as opposed to the fast reducer which
I had used previously. I want to try spray out as slick as possible. I shall be using the 1.4 tip on the devilbiss gfg-670 plus gun.

Thanks ... X

baddbob 12-01-2005 07:29 PM

Wow, that's a really good example of what temperature can do for the viscosity. You can imagine what headaches can be created by using too much reducer in cold paint to get the viscosity right. I was kinda hoping that Barry would chime in on this post and give his nickle on viscosity especially with some of the more solvent poppin prone clears of today. More solvent can sometimes come back to bite ya in the end with more chance of pop and possible dieback problems. But then again I know Milo reduces it how he likes it but I think he's also fond of higher air pressures when applying, nobody can deny that his work looks really good so he's got it the way he feels is best. Personally I try to stay fairly close to what the manufacturer recomends reducerwise. Usually less reducer means more retained gloss after clear. One example is Dupont's Chromaone- spray it without reducer (solid colors) and the gloss will be much more than if it had been reduced. Bob

x711 12-01-2005 08:11 PM

Bob, sure surprised me, Its all very interesting indeed. I think the trick is to have
your temperature where you can use it for a good period of time. Then configure
your paint so its more suitable for that temp.

If you are new to this and I am, your pretty much dead in the water if you
dont know the Viscosity of the paint as at that point its only a guessing game.

Thats not to say you cant make it spray correctly. I just like to be more informed and try elimate possibility of error up front in advance until I build
experience.

I agree that Milo has it down, fair dues to the guy he knows what he is doing
and is real helpful to others on here too. This place is a goldmine such a cool
Board :)

Thanks .. X

Bee4Me 12-01-2005 08:47 PM

AH HAH,
You ARE a rocket scientist aren't you? :D

I have to give your due, You have tried to answer the 64 million dollar question and done a good job of it too. :thumbup:

The Zahn cup is a nice tool but can get you into big trouble as you've (I hope) realized. Reduction is a good thing but like booze need's moderation and common sense.

I used one a few times but ended up just staying within the Manuf's guidelines for the product for the most part and had much sucess doing so.
It just got to be TOO much measuring and fiddling around.I just want to paint.

Glad you got what your looking for.

Mike.

x711 12-01-2005 10:14 PM

Ha, Ha Mike, good to hear from you. Well if nothing else I sure am
persistent :) lol.

Hey, Im new to this so while the Zahn cup might be a little over kill
I am now in a position to eliminate the variables. Now im sure I will still
have to tweek the process no doubt about that but what I have is a 1/2 decent reference point to move forward with.

It kind of cool really. Knowing the viscosity of the material one is spraying
can help shed light on problems down the road, assuming the manufacturer
got it right that is, Yikes hope they did :)

Using the cup aint too bad really. Just pop it in the liquid see how it flows
out, reduce as needed but dont over reduce. Do it a few times then I can move on to Milos method using the stick drip test.

I just need to get a better feel for it so me thinks I am on track.

Thanks X.


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