Converting Waste Pigments into Art Supplies

System to turn wasted retail store house paint pigment into (almost) free art supplies.

Similar projects worth following
Stores that custom mix house paint refill their machines with containers of pigment. Due to the nature of capitalism, those containers are poured out, but usually not scraped or completely drained. The remaining pigment isn’t worth the labor cost to completely empty it, but to anyone who’s ever worked with watercolors, the residual pigment in one quart jar would be enough to paint with for years. And since there’s always a school that barely has an arts budget, or community group that can use art supplies, it seems like a great opportunity to reclaim all that residual pigment and turn it into art paint.

For smaller stores, pigment comes in 1 quart cans or jars, for larger stores it’s containers up to 5 gallons. For the donor businesses the effort would be minimal - put the cap back on and keep the empties in a box until whomever is going to convert the pigment can pick it up. There’s value in making donation that easy.

Although most pigments can be converted into watercolors, gouache, oils, acrylics, encaustics (and probably others), I’m developing my formula for watercolor first because you can make a lot of paint relative to pigment volume, the other ingredients are pretty inexpensive, and it can be stored dried in pans, as opposed to having to be kept wet like acrylics or oils.
I’ve already successfully made hand milled watercolor with gum arabic, gylcerin, and honey. As beautiful as the historic process of hand worked glass mulled paint is, that isn’t practical for busy art teachers, or the kind of people inclined to work with community organizations.

Right now my focus is on a small desktop three roll milling machine. It’s a common way to manufacture paint, and produces consistent, good quality results quickly and with low physical labor involved. To buy a milling machine starts at around $1000 US, so I have a lot of room to undercut that with my open source version. Since the pigment is already pre-milled to very small particles the equipment will primarily need to make the ingredient mix consistent and eliminate any larger chunks. I can’t find any precedent for DIYing a three roll mill, so I’ll be completely working from scratch, and an accessible desktop milling machine could be useful for many kinds of project. I also have some ideas for add-on tools to create after the milling process is established.

My conversion system will to be open source with the easiest to source materials possible. I’m using an Ender 3 printer (sub $200 cost) to make any parts that aren’t commercially available.

Since I’m already using a 3d printer, I’m also printing my watercolor pans with it. They are weirdly expensive to buy, and right now I’m getting about 644 half pans (the most common size) per 1kg spool of PLA. I buy my PLA in bulk for $10 US per kilogram, so each costs about $0.015 in materials.


- Finalize Recipe/Technique
- Design and Prototype Milling Machine
- Design Storage (Watercolor Pans)
- Documentation/Parts List/Printer Files/Build Instructions
- OSHWA Certification

  • So Many Empty Containers

    technoplastique06/17/2022 at 15:46 0 comments

    One of the challenges with this project is how many empty plastic paint cans (or other containers) it generates. They are very sturdy and well sealed containers, so there's a lot that can be done with them. I've found a few solutions so far:

    - The brand I'm working with now is made of #5 plastic, which is polypropylene. Because I'm rinsing them out, I'm making them clean enough to recycle, and that kind of plastic is accepted for recycling in my city and many other places. That said, I know that recycling still has limits and whenever possible, reuse is a better option.

    - When making acrylics or oils I could just use them as containers for the new paint.

    - I'm using them to store all the components of the paint I'm making now. The gum arabic/honey/glycerin mixture is all suspended in water and needs to be stored sealed. Empty cans are great for this. I'm also using them for dried pigment while I accumulate it before making a batch of paint.

    - Polypropylene can be made into printer filament, and could potentially be made into paint pans for watercolors. The downside to this is that my containers are black, and white pans are preferred to show the color more clearly.

    - Metal cans are much easier to recycle in many areas, so for systems that use metal cans they could simply be taken to a metal collection facility.

    - Clean empty containers could just be listed on craigslist or facebook marketplace for others to collect and use!

  • Dehydrated Pigments and Milling Machines

    technoplastique06/11/2022 at 21:59 0 comments

    All of the paint store pigments I know about at this point are blended into some kind of liquid, most often water, though that’s not the case for pigments used in oil based paint tinting. For now I’m focusing only on pigments for water based paint tinting (latex, acrylic, etc.).

    My current process is to dehydrate the pigment, and then rehydrate it. There are a few reasons:

    - Dehydrated pigment takes up so much less space. The space needed to store nearly empty quarts adds up quickly. For efficiency I like to accumulate quite a few of a given pigment before mixing it with binder, and I'm still in my prototyping phase. The neighborhood hardware store I’m working with easily generates 10-20 “empties” per week. My metro area of about 170,000 people has 8 stores that I could be collecting from, most of which are bigger. If I was seriously making paint I could be picking up hundreds of empty quarts/containers a week (hopefully with the help of a like-minded team.)

    - If I’m dehydrating, I can rinse the cans out onto my sheet, instead of meticulously hand scraping. This is a huge time saver, and eliminates a really tedious task.

    - It’s easier to create reproducible recipes with dry pigment. Working with weights instead of volumes is significantly easier and more accurate. It also opens up the potential for blending pigments to create other colors.

    - If I want to use pigments to make oils or encaustics I’ll need them to be nearly moisture free.

    - When making watercolor pans, the usual process is to fill part of the way, let it dry, fill more, let dry, and so on. Most watercolor pans have 3-5 layers in them. Adding binder that’s dispersed in water to pigment that’s dispersed in water makes a paint with really high moisture content. This would result in either lots of fill layers, and/or really long dry times.

    - Dry pigment is much more resistant to mold when being stored. For short term work mold isn’t a big concern, but if you allow hydrated pigment to sit for a while before processing it would become a concern.

    I received a very helpful comment from pmaitrot saying, among other things, that the three roll mill is overkill for pre-dispersed pigments. I totally see where they're coming from. My choice to go with this option has a few layers.

    First, I've tried to hand process dried pigment with hydrated watercolor binder, and I was able to do it but it was *work*. It took a while and a lot of physical effort to get to a paint I really wanted to use. They recommend trying a dissolver disc, and that's something I will be experimenting with.

    They also suggest looking for a used milling machine. In Germany they found a used one for about 50€ which is fantastic, but in my searches I'm rarely able to find one in the US for less than $1000, the cheapest on eBay right now is $929. And even if I was able to score a cheap machine, that still doesn't address my intention to make this into an easily reproducible system. There's a huge amount of pigment being thrown away every day, and there's probably an even larger amount of underfunded arts programs that could benefit from this. Lots of localized processing means less wasted time and transport, and more community ownership.

    The other reason I'm thinking of going all in with a milling machine is a really about human nature. Sure, people will start with my instructions and recycling prepared pigment. But then someone will think how holographic glitter or iridescent resin pigment dust would make a really cool paint. Someone else will have some dried turmeric that's such a pretty color, and could that be paint? A dissolving disc probably wouldn't be enough to get all of those things made into paint.

    And finally, a machine built by the owner is also maintainable by the owner. If something goes wrong, they aren't trying to figure out how to repair or replace an obscure piece of lab equipment, they can just go buy a new dc motor to swap out with the bad one.

    At this point...

    Read more »

  • Sourcing Components for The Milling Machine

    technoplastique06/11/2022 at 05:50 0 comments

    While a three roll mill is a fairly straightforward concept, to function well they have to made to pretty specific technical specifications.

    Each roller turns in the opposite direction of the one before it, and at variable speeds.

    Three Roll Mill

    The gaps between the rollers must be very small - almost touching, and adjustable. Ideally the material is run through the mill, then the roller gaps are tightened, and the material is run again, as many as 5 times.

    For most mills the gap between the rollers helps to break down the pigment into smaller pieces. In this case the pigments are already milled small enough that this won’t be a major concern. We’re primarily turning a chunky and inconsistent mix into a smooth and consistent one.

    I’ve added for myself the challenge of trying to build this on the lowest reasonable budget. My first prototype will be built using a raspberry pi pico, a motor shield, power supply, and dc motors. A pico seems capable of controlling 4 motors, and this will only require three. This leaves a motor slot left over for controlling the gap adjustment. I have a variety of ideas on how to do that, but they will require testing. I’m sure that will evolve over a number of attempts.

    The biggest sourcing concern for me is to find stainless steel rollers that are readily available for anyone building a milling machine, mountable for precise turning and adjustment, and not impossibly expensive. I have two options I’m considering at the moment. The first is steel rolling pins (the kind for cooking). They’re readily available, but may be difficult to mount without drilling additional holes. The second is stainless steel pipe couplings. The advantage to couplings is that they are threaded on the inside in standard pipe thread, allowing for a variety of ways to mount them. The disadvantage is that they are most commonly available 1-2” long, which is too short for my needs.

    So for now my first move is to get a functional prototype working, so that I have something to build on and improve.

View all 3 project logs

Enjoy this project?



DalChrome wrote 07/09/2022 at 10:15 point

Hi, Would you be able to tell me the pigment names/numbers and the percentages in the solutions please. I am working on a project that uses pigments and even though I am not in the US, it would be good to make mi project compatible with the supplies you discovered.

  Are you sure? yes | no

pmaitrot wrote 06/11/2022 at 08:50 point

Hi, Phil here. I am a chemical engineer who owns a company that does a lot of work with pigments. If you need any help, feel free to contact me. I have a lot of tips for you. For starters, the pigments that are supplied for those in-strore tinting machines are already pre-dispersed and do not really require three-roll milling anymore. It´s not because of finer milling of the pigments but more about better dispersion in the required medium. As I said, the pigments you use are already pre-dispersed and stabilized. You would be better suited with a simple dissolver disc set-up. It´s just a special disc you can get on aliexpress and a motor. If you still want a three-roll machine, take a look at ebay or pharmacies that shut down. Here in germany for example every pharmacy that makes body creams with pharmaceutical ingredients needs a thre roll machine by law and they are really cheap to get from older pharmacies and they are really tiny and perfectly suited. I got mine for I think 50€ and it´s at least 50 years old but like new ;-). Take a look at my website and contact me if you like. Cool project!

  Are you sure? yes | no

technoplastique wrote 06/11/2022 at 22:02 point

Hi Phil, thanks for your comment! I really appreciate you sharing your experience, and I will probably take you up on your offer of help :) I was going to just reply here, but I ended up with a lot of thoughts so I rolled them into my latest project log. Take a look if you have time, and please feel free to keep the feedback coming!

  Are you sure? yes | no

Mùminu wrote 06/09/2022 at 12:50 point

wow, very interesting. Looking forward to see how it's going

  Are you sure? yes | no

technoplastique wrote 06/11/2022 at 05:55 point

thank you!

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates