Choosing a Scale for Color Mixing
Finishers discuss the equipment issues involved in weighing and measuring colorants for creating custom tints. June 28, 2006
Question
What size/capacity scale do I need for mixing colors? I will be mixing 1 gallon of lacquer. I don't want to invest in a tint dispenser, so I will be measuring the dyes or pigments. Do you get a scale that is big enough to handle the weight of the gallon and then add by weight, or do you measure the colors by weight and then add them to the gallon? I am not thinning the lacquer, so how do I get all of the color out of the cup?
Forum Responses
(Finishing Forum)
From contributor G:
A scale with enough capacity to weigh a whole gallon won't be fine enough to register 10ths of grams. Get a set of good glass beakers and a scale that reads in .001 gms with as large a capacity as you can afford. When formulating, you tare the scale with a beaker, then put in your colorant. Weigh this and you will have the before number, which you record on your Rx sheet. Do your color matching, using the pre-weighed colorants. Weigh all the beakers again when you're done and the difference, the after number, is the amount you have put into the match. To remake this color, weigh the specified amounts of each colorant into an empty gallon and top up with base. Shake well.
From contributor J:
I have a sartorious scale PMA7500. 7500grams to .1grams. It is explosion proof. I think 7500 grams is about 16 pounds. They retail for $2500. If I need a gallon of stain or paint, I usually start with a half gallon of base just in case I add a little too much of something - then I can double it up and hopefully not wreck any stain. Add what I think will get me close, write it down, stir, wipe on some wood, see where I'm at and continue. I have never had a problem mixing anything this way, dyes or pigments. Buying a scale that reads 7500g-.001g would cost, I'm guessing, about $10,000. You can get them cheaper, but then you would have to put your color in beakers or cups and then clean every bit of color out of them and add to your base. It would be a pain and take forever.
From contributor K:
I recently purchased a 5500g scale from oldwillknottscales.com to do exactly what you want. It reads in 1/10g and has the capacity to mix full gallons. It is an imported unit, and not top of the line, but for our limited use, it is the ticket.
From contributor T:
A 5000 gram scale is usually fine for what you are doing. They will cost $500 to $1200 depending on what bells and whistles you get.
From contributor S:
When making up formulas for matching purposes, I only use about 1/2 a litre of base material. I also prepare dilutions of my tinters in the clear base material, so that 10g of the diluted product contains 1g of tinter. This means I can work accurately on a small scale and if I cock up, I am only wasting 1/2 a litre of product.
From contributor M:
Thanks for the help. Man, these things are expensive.
Contributor S, I may be dense here, but I still have questions about the way you mix. Let's say that you mix your solution, starting with 500 ml, then add your colorant. Now you have your mix, and you know how much colorant to add to the whole gallon (I measure in metric, but it goes into a gallon). I use disposable plastic beakers. So when I pour the pigment into the beaker, there is a certain amount that stays in the beaker. The original mixture included the product, but the new mixture does not. What do you do to get all the colorant into the gallon? I won't be thinning this. In the past I have rinsed with thinner. And when I add lacquer to the beaker, there is still some pigment left in the beaker. Maybe I am being too concerned here, but we are using white, and it is to have a certain transparency about it. Too much or too little seems to throw the color off.
From contributor G:
Read again what I said. Which is not what contributor J thinks I said, either. You do not need to clean out the beaker. You need only to know how much is used in the Rx. Which is the difference between the Before and After weights. If you formulate a pint instead of a gallon, multiply by 4 to get the gallon Rx.
eg:
Start - 100 gm red
100 gm blue
Finish - 75 gm red
90 gm blue
Plus base
Result - to make that amount of purple, you now know that you need 25 gm red and 10 gm blue. Only scraping required is to put leftover tint back in its can.
From contributor G:
Oops - I also use metric and obviously don't know my pints and quarts very well.
From contributor S:
Basically, all weighing is done into the final container, so there is no need to transfer from a weighing container to the final container. If you use the latter system, you need to prepare the weighing container by pouring some of your base material into it before you start. This is used to coat the sides of the weighing container, preventing the tinters from sticking to the container. The weight of this base material is tared out along with the weight of the container itself.
In the car spraying business, all colours are done by weighing out into the final container. The difference here is that they don't use tinting pastes added to a white or clear base, but actually have a range of primary coloured paints that are then mixed together to get the final colour.
