asked for "viscosity cup" -- got a blank look

[Wild Turkey]

Went to the local paint/body supply house and asked for a "viscosity cup."

Got a real blank look from the young guy.  He asked the older guy who said he'd never seen one in stock.

Went to the other place in town that sells auto paint and had similar response.  Guy in office comes out and pokes computer and finds one for $75


Said no thanks and as I left heard him explaining how they work to counter guy.

Do folks not use them anymore?

[Splinter Puller]

https://www.amazon.com/TCP-Thickness-Vis...s=FORD+CUP

$10

This is a big reason why I am a fan of Amazon.  I've looked locally at the same types of places you did for quite awhile.

[fredhargis]

Home Depot has them (online) for the same price, though I suspect they would gouge you for home shipping. There are some precision ones that may run $75, as opposed to the home owner styles.

[Snipe Hunter]

I've never seen or used one. Most car painters make the assumption that the stuff our suppliers are selling can be sprayed without too much trouble. I can't imagine a time I would need one.

[jteneyck]

You need one if you want to know what the viscosity is of the product you want to spray, and if you want to adjust the viscosity to some known value. Adding thinner until it looks right might work for someone who sprays for a living, but not for me.

For $6 - 10 it's a cheap investment that can save you a lot of grief. I wouldn't be w/o one. I use a Ford #4 cup.

John

[Snipe Hunter]

You need one if you want to know what the viscosity is of the product you want to spray, and if you want to adjust the viscosity to some known value.

Well sure but when a car painter mixes his paint, the proper amount of reducer is listed in the formula. Messing with the amount of reducer does strange things to automotive paint. About the only time I would ever change reducer values is if I were spraying a formula with inerrant poor coverage like a metallic red or blue or even a solid (non metallic) white. I might leave a little reducer out to get better opacity. Or, I might use a faster or slower flashing reducer depending on the temperature.

I can understand why a woodworker might want a viscosity cup for wood finishes but I wouldn't think he could buy one at an auto paint supplier when they would really have no reason to carry them.
 
What I also don't understand is why wood finish suppliers don't spell out their mix ratios better, whether it be on the can or on the material data sheets.  I can understand why they don't spell out tip sizes because all guns are different but at least they could provide a simple base-line. Like 4 parts finish to 1 part lacquer thinner etc. That would take 90% of the guesswork out of thinning. All you have to do at that point is tweak it a little to get it too shoot and lay-out right. It would be very simple to do.

[Rob Young]

 
What I also don't understand is why wood finish suppliers don't spell out their mix ratios better, whether it be on the can or on the material data sheets.  I can understand why they don't spell out tip sizes because all guns are different but at least they could provide a simple base-line. Like 4 parts finish to 1 part lacquer thinner etc. That would take 90% of the guesswork out of thinning. All you have to do at that point is tweak it a little to get it too shoot and lay-out right. It would be very simple to do.

Some manufacturers do.  Two that I know off the top of my head are General Finishes and Varathane (or whoever it is that owns the Varathane name).  In the case of GF, I believe they also give the viscosity as determined by a #4 Ford cup.  The info I found from Varathene was in centipoise.  So in the end, you need either the conversion formula or one of the charts.  Both listed the recommended nozzle size for HVLP gravity and pressurized cups as well as airless systems.

In the case of GF, I think it is on the label.  For the one Varathene product I used (their waterborne spar goop) it was buried in a datasheet.

Ultimately, the cup is more useful for determining appropriate gun configuration / dilution so that you can get repeatable results with the same equipment and finish combo on multiple projects.  The absolute values aren't important, repeatability is important.

Anywho, the $10 cup from Amazon is useful.

---

On a similar (but ultimately more positive note) I asked for a wet mill gauge at my local Sherwin Williams store.  First clerk had no idea what I was asking for and I started to describe it.  Second clerk (who seemed to be more senior in rank) knew exactly what it was and as he was asking me how many I wanted, reached under the counter and pulled out a stack.

Probably not a critical item to have but it is kind of interesting to use when figuring out how fast to sweep and fiddling with the gun settings.

[Bope]

GF lists needle sizes on the label for pressurized cups. They don't give viscosity. You still need to adjust if using gravity or siphon guns.

[Rob Young]

GF lists needle sizes on the label for pressurized cups. They don't give viscosity. You still need to adjust if using gravity or siphon guns.

Look at the data sheet : https://generalfinishes.com/sites/defaul...-07-28.pdf for the viscosity. Yes, the label just gives the needle sizes. This is what happens when you try to work solely from memory...

(One example that I know of, not certain if ALL their data sheets have the viscosity rating.)

[Wild Turkey]

Lots of good information in this thread.

The big reason I wanted a viscosity cup is that I build stuff using steel and want to paint it with oil-based enamels (like Rustoleum) and all they say is "thin up to X%" which leaves lots of room for oops.

And even using wood finishing stuff I'd like to know how one compares to another so I can know what to expect when I start shooting.  One less variable is a step in the right direction when you're learning new techniques.