The Stovebolt Site Forums The Shop Area Paint and Body Shop Paint mixing by weight?

I need a little help. I have the data sheet for a couple different types of paint that call for mixing by weight. How does that work. I have one that says 15 parts to 1 part. I need to mix small quantities and can't figure this one out either. 15 ounces to 1 ounce gives me a half a quart of paint and I don't want to shoot a whole quart but don't know how to extrapolate this down and have a correct mixture. Do you use a scale that measures in grams. Slicksand by evercoat is one of these and the other is a ppg product.

Use one of the inexpensive electronic scales favored by jewelers and dope dealers. They're available on Ebay for just a few dollars. I measure reloading powder that way, and most of the scales can be set to measure in ounces, grams, or even grains as the standard. Use a small paper or plastic cup as a container, and set the scale to measure "tare weight" which ignores the weight of the container after it's placed on the scale.
Jerry

It's difficult to grasp the concept of PARTS, but once you get the hang, it's easier than you think. 15 oz to 1 oz is 16 oz of material. 7.5 oz to .5 oz is the same thing, only half the material. 3.75 oz to .25 oz is the same thing only half of that. You don't need a scale, just a calculator. When they say "by weight", they have figured out already how many Ounces of this, is necessary for how many ounces of that.

Most automotive paints are measured in Parts. The paint cups that you purchase for measuring even have the most popular weights or parts printed on them.

Clear as mud right? Do some searches on Automotive Painting/Parts. all sorts of explanations will show up. Personally, I would like someone to make an online calculator where you put the number of ounces you want, and how many of each part is required, and it just tells you. Haven't found that yet. Good Luck!

I must have been doing it all wrong- - - -those 30-something years we mixed paint at the body shops I owned/managed using a scale! Deve, thanks for correcting my decades of actual experience!
Jerry

A fluid/liquid ounce (measured in a cup or with a measuring stick) is not necessarily the same as a weight ounce (avoirdupois ounce).

If the components to be mixed have similar densities, then mixing them by weight/scale or mixing them by volume would result in the same ratio.

My PPG sheets show mixing by parts/volume (not weight).

Most likely this does not really matter because the ratios are probably not very strict/critical relative the error of mixing parts using a scale vs using volume.

For small mixes, I bet that using a scale would be far better than trying use volume (no matter what the densities of the components). The errors in trying to measure small volumes are surely more than the density errors from using a scale.

Ever watched a paint supplier do a custom tint for a factory color? It's definitely done by weight, at least at every shop I've been associated with. Put the mixing cup on the scale, and run the specified amount of base color or tint in, then move on to the next color. If 1/4 pint of a specific color is needed for a spot-paint job with a trim gun or an airbrush, no problem, and no waste. Those tinting colors are E$$PENSIVE!
Jerry

If you read the original posters post, he is talking about Slicksand. He isnt even at the final painting stage. Use a cup and be done with it. First step is learn how to do the math in PARTS.

If you are doing final paint, you arent mixing it yourself. Your paint supplier is doing it with the properly calibrated scales for this application. In the printing industry we do mixing Pantone colors all the time and we use very calibrated scales. I do this myself. But the end user never mixes their own. If they do, and they dont know how to mix using parts, they are on their own.

The best advice for the common restorer is to get your final paint mix from a PPG professional (or equiv). Mix your own Slicksand, PPG Urethane primers, etc, etc yourself using your mixing cup. Dont go out and buy some uncalibrated scale and think you are qualified for a process you may have to repeat somewhere down the line. No disrespect Jerry. I agree with you, but in this case, he's over his head. Good idea to help him recognize this to avoid some of the mistakes WE have made in the past.

After using my Pyrex measuring cups for decades, I finally got tired of the cleanup and adding up the units.
Now I get mixing cups from my paint supplier. Plastic, around a quart, that have a series of proportion scales printed around the outside. 4:2:1 or 3:2:1 or 4:2:1:1 and so on.
You pick the scale that matches the paint you are using and with in the vertical column for that scale are 3 or 4 columns of numbers.
If you are mixing 4:2:1 for example, you pour in paint until the first column reads say 8. Then you add thinner until the second column reads 8, then add hardner until the third column reads 8.
Perfect 4:2:1 mixture, no math, no cleanup.
Sometimes we do get smarter when we get older.

Deve, I think I had figured some of that out. The problem for me is how do you measure .25 oz of catalyst or the smaller amounts of paint like 3.75 oz. I can't find any measuring spoons that go that low. The smallest measure I can find is 1 ounce. I'll have to go get one of my paint cups (PPG) and see what the other posters are talking about using parts. I'm learning a lot. Thanks everyone for helping.

My paint store has little bitty disposable mixing cups just for the small amount you want to make.

Lets stick with one product at a time.
The quick sand or evercoat featherfill g2 polyester high build primers are great as long as it's used and mixed correctly.

22cc liquid activator(hardner) per 32 oz of primer
or
.68cc of mekp(liquid hardner) to every ounce of quick sand primer.
You could use a hypodermic needle for the hardner and a paint mixing cup for the primer.
the paint store most likely has a small mixing cup measured in cc's as well.

tim

Well you will love this I went to the PPG dealer and asked if they had scales or cc cups, and how to measure the MEKP catalyst. The answer: "We only have oz cups, don't know about scales and let me show you how to measure the catalyst" So she takes the little bottle turns it upside down and commences to show me where to mark it off with a marker at the 3/4, 1/2 and 1/4 areas. How's that for precision.

The scale that they are referring to is the same scale that is used to mix a color.
Some of these scales have a program on them that will have the mixing ratios set up in them so that you can add catalyst and/or reducer right on the mixing scale.

We have this set up in our shop, it will also keep track of material used on each job.
I recently changed jobs, Im now working in a shop that uses PPG, and our scale is set up for that.
I havent got used to it, Ive only used a mixing scale strictly for mixing a color. I like using the mixing cups with the printed ratios on them to add catalyst & reducer, & they are scaled down so you can mix smaller amounts.

The numbers on the cups are also called a scale.

The easiest thing you could do is find a mixing cup that has your ratios on them, then your good to go. Unfortunately not all cups have all ratios on them.
If you cant find one , try & find one that is close.An example: I see you are looking for a 15 to 1, I have cups here that will do 8 to 1 , if you can figure out how much more to make the 8 a 15, it will work.

I just took a look at one of my mixing cups, to get a 15 to 1 ratio you can use the 8 to 1 scale on the cup.

The first column on that scale is for your first ingredient.
The second column is for the second ingredient.

To get a 15 to 1, you want to double up on the first ingredient.
So if you double up the first ingredient on the 8 to 1 scale, that makes it a 16 to one.
That would mean pour to the second line up from the bottom on the first ingredient, then on the second ingredient, pour to the first line up from the bottom.

That makes a 16 to 1 ratio.
To get a 15 to 1 , pour the first ingredient just below the second line up.

If you need more, just double up on what you just did.

I use the quart cups, you can also use the smaller cups with the same numbers on them, they just make smaller amounts.

Ok ,I assumed you knew the small bottles were marked.
glad you figured it out.

That's how my local PPG dealer does it. Watched them do it several times. The only time I've seen them do it differently was the last time I needed paint (got hit in the rear fender in the parking lot at work), had the correct code for the paint. After they mixed it, we went out to the truck to make sure it was right. Seems the color had faded a bit since the truck was originally painted. The guy mixing the paint took the cans of the appropriate toners and mixed it by eye right out in the lot. I was shocked at just how much PURPLE (??!! ) there is in that particular shade of blue.
However, while mixing the color was done by weight, mixing it to spray was done by volume. I got mixing cups from the paint dealer with the correct ratios marked on it, in this case, it's 8-1-1.

It's been a LONG time since I custom mixed paint. In trade school we mixed by volume. The machine had a rod with a pointer on the end that extended into the can (no plastic cups back then). The formula called for X amount of Y color so we'd set the pointer at X & fill the can until it just touched the tip of the pointer. We'd then set for the next color and so on through the formula. Later on when I was painting Cessnas we mixed by weight. Same theory but using a scale instead of a pointer.

Ok so as I read this thread I think we are talking about two different things. If you are mixing Color. It is done by Weight. Now if you are talking about Mixing color and reducer for spraying then you mix by ratio. Two totally different things.

Now for those of you that have mixed color by weight. How many of you have used a shadow scale?

Not for paint mixing, but the scale we used for connecting rod weight matching and assembling bob weights for crankshaft balancing was a shadowgraph calibrated in fractions of a gram. ( A dollar bill weighs approximately I gram, so a +/- 1/10 gram tolerance is pretty accurate!)
Jerry