1

Not sure, if possible, but from my understanding, we often buy resin and hardener from shops, and then mix them before pouring into mold tray.

So, I was wondering if we can use common household ingredients (such as soda carbonate, white glue, the list is non exhaustive but are items that is commonly found in a house) to create non-toxic or less toxic resin, to be used in mold tray.

So, is it possible to use common household ingredients to create DIY resin?

  • You might be able to use other materials, depending on what you want to obtain. – virolino May 29 at 10:13
  • That's the missing portion of this question, what is the objective? One usually has parameters to be met, mechanical, chemical, etc, but this question leaves so much open and unanswered. – fred_dot_u May 29 at 22:07
  • What are you making a mold of and what material are you trying to cast? The resin can damage the article that you are trying to make a mold of, and the material which you are trying to cast may break down the mold. These are both important when trying to find the material o use in the mold. – Lilibete Jun 6 at 5:22
  • To answer this in a useful way needs more detail on your actual objective. If by resin, you mean a 2-part clear polymer optimized for casting, the answer is no, you can't make anything similar with household ingredients. However, there are lots of materials you can make from household ingredients that may be perfectly fine for a specific task. If you describe the kinds of projects you have in mind, that will identify the characteristics that are important. From that, we can identify things you can make that might fit the bill, or be able to know that you can't do it with household ingredients. – fixer1234 Jul 29 at 1:25
4

According to Wikipedia, resin is:

In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on naturally-occurring resins.

The article references plants which secrete resin for protection. The synthetic aspect of resin covers epoxy and polyurethane resins, more commonly used for casting.

It is likely that you would be unable to create sufficient quantities of plant based resins for casting in molds.

As a more generic answer, one could use gelatin to cast items, but the physical properties may be insufficient for your purposes. Gelatin is not known for durability nor for physical strength.

2

People have suggested many kinds of household materials that can be used for casting. If you really want a resin that looks, feels, and acts like plastic, there are a few options.

  • PVA glue (common white glue) will dry to a soft plastic, but with tremendous shrinkage, and it will redissolve if it gets wet, and can turn cloudy from absorbing humidity. The shrinkage and drying time makes it impractical to cast 3D objects with it in one step. But you can coat the mold with a layer, let that dry, then add another layer. Repeat until you have a thick shell (and leave that hollow or fill it with something), or continue to add layers until it's solid. It will be expensive, because you will need a ton of glue to yield a solid piece of PVA.
  • You can improve on PVA glue with what's referred to as "cold porcelain". There's endless information and tutorials online, but it's basically a mix of PVA glue and gelatinized starch, plus a tiny amount of a conditioner, like mineral oil or glycerin. It can be enhanced into an even tougher, more plastic-like material by adding a little stearic acid (used in manufacturing many cosmetics and personal care products, and available to hobbyists for candle-making, so it could be a household ingredient).

    Cold porcelain has a consistency more like dough, so it's typically used like modelling clay. But you can press it into a mold and get fine detail. It shrinks a lot, so if matching the original size is important, you can do it in layers. Line the mold with a thin layer, let it dry most of the way, add another layer, repeat. The shrinkage will be mostly in the thickness.

    Depending on the additives, it dries translucent or white, rather than clear, or you can add food coloring to it to make a colored plastic. You can reduce the shrinkage by mixing in a filler. However, that makes it much stiffer. You can also start with less water in the mix for the fill layers, which will reduce shrinkage. Another trick is to start with less water, more starch, and not gelatinize all of the starch. Once it's in place in the mold, you zap it in the microwave to gelatinize the remaining starch and it sets up in place as a solid.

  • If you want to experiment, you can make a bioplastic based on starch. There are starch-based plastics and foams used commercially, but they have additives and processing steps that would be hard to replicate at home. What you can make at home is rubbery to hard based on the ratio of ingredients. It shrinks a lot so it isn't practical for most applications, but it's a fun material to play with.

  • From ancient times Until World War 2, casein plastic was "the" plastic. In the late 1800s, it was discovered that exposure to formaldehyde turns it into a tough, insoluble material that people think of as plastic today. But even without formaldehyde, it is a moldable resin you can make at home. The crude, cottage cheese stuff covered in how-to links on the Internet aren't really ready to use. The instructions don't explain that the casein needs to have the impurities removed to become a putty-like material that's good for molding. See https://www.youtube.com/watch?v=BnXGZKCrktE for an explanation of how to make the good stuff at home. You can also turn it into a flexible rubber by adding some sulfur. See https://www.youtube.com/watch?v=VzEujd7iEHU.
  • Hot melt glue can be used for casting as long as the mold can tolerate the heat (like a silicone mold). It will capture fine detail. It does shrink a little bit, though, so if you want to retain the size and contour of a thick mold, cover the mold with a layer, let it cool to the point that it's still good and warm, add another layer, repeat. The clear sticks aren't "optically clear", so you won't get a result that looks like glass. If you want colored plastic, hot melt glue sticks are available in endless colors (including gold and silver), and things like glitter.
  • You can mold with actual recycled plastic rather than two-part resin. PETE, which is the plastic used for most water, soda and juice bottles, is a good one because it melts into a liquid that flows well into the nooks and crannies of an open mold (which should be made of silicone rubber to tolerate the temperature). You can verify the type of plastic from the recycling symbol if you aren't sure.

    There are lots of online tutorials on the details. Here's one on using bottles: How to Melt Plastic Bottles for Molding. Most plastic you recycle won't be a pure resin, it will have additives to give it particular properties. That will affect the melting temperature, and your oven temperature may be inaccurate. So a certain amount of process adjustment is required.

    The approach described in that link is to melt the plastic and pour it into the mold. Another approach is to melt the pieces right in the mold. Over-fill the mold with the plastic chips and heat it in your oven. As the plastic melts, the liquid will take up less volume than the solid pieces, so you can add more plastic.

    If you're careful to build the temperature and then keep it at the minimum required to melt the plastic, there won't be much in the way of fumes. But if you try to rush it with a higher temperature, some of the plastic will start to break down and you'll get some nasty smells. It's generally best to use good ventilation.

  • You can also cast polystyrene at room temperature using household ingredients. There are lots of online tutorials for dissolving Styrofoam, but the following approach works best for good quality casting, and doesn't involve toxic fumes.

    Collect clean Styrofoam. White foam, like from package inserts, and styro cups and trays, will make almost clear polystyrene. You can make colored plastic by using colored Styrofoam. Meat is often packaged on black styro trays. Egg cartons often use colored Styrofoam (but cut away any parts with printing). Colored Styrofoam will become a solid, opaque color. You can make tinted polystyrene by adding a small amount of colored Styrofoam to clear (white). This is easier to control if you create the resins separately, then mix them and observe the color. You can start with pieces of polystyrene instead of Styrofoam, but that will take a long time to dissolve.

    Styrofoam will dissolve in endless solvents, but most will not produce a good casting resin. Among other problems, and toxic fumes and fire hazard, there will be a lot of shrinkage and air bubbles trapped in the finished plastic (apparently from the evaporating solvent, since it happens even if the polystyrene solution is low viscosity and ages until no bubbles are left from the Styrofoam). Limonene, a solvent made from citrus fruit, has all the right characteristics for a good finished product. It's widely available as a general purpose cleaner.

    Styrofoam is 95-98% air, so the volume of polystyrene is only 2-5% of the foam you start with. Styrofoam dissolves much slower in limonene than in solvents like acetone, so rather than a spectacular show of reducing Styrofoam to nothing before your eyes, you need a large airtight container, like a plastic paint storage bucket, to produce enough polystyrene to cast.

    Fit as much Styrofoam as you can in the container, and pour a few ounces of limonene over it. Seal the container, wait half a day, and check it. Push any chunks of Styrofoam into the liquid. If you will need more polystyrene, add more Styrofoam. If the dissolved Styrofoam is very thick (viscous), or there wasn't enough limonene to reduce the Styrofoam to a puddle of goo, add a little more limonene. Once everything is dissolved and you have a little more than you will need, you can play with the consistency.

    You want to start with a thick syrup, like honey or molasses, and you want all of the air from the Styrofoam to have dissipated so there are no bubbles in the liquid. Over the course of a few days, the limonene will diffuse evenly throughout the resin. Some of it will evaporate (even in the sealed container). The resin will become a clear, uniform liquid

    As the limonene evaporates, the resin will become a gel. You will be able to pull it away from the side of the container and it won't be sticky. Prior to this point, some of the resin volume will be excess solvent, so there will be shrinkage of that percent when it dries. Once it turns into a gel, there won't be much shrinkage; what shrinkage there is will be mostly in thickness.

    Scoop the gel into the mold. It will slowly flow into the nooks and crannies. Wait for it to flow, then add more gel until you completely fill the mold. Give it about a week for all the limonene to evaporate (you'll know it's finished when there's hardly any citrus aroma). Then remove it from the mold. The surface that was exposed to air should be very hard. The surface against the mold should be solid, but may still be a little soft. Set the casting mold-side up and let it dry for a few more days, especially if that side has any citrus aroma.

1

Depending on what you need to obtain, and also depending on quantity, you might want to think of other materials.

Note: some of the ideas below require you to have at least one of the following:

  • special knowledge;
  • special skill;
  • special tools.

Alternative materials:

  • some kind of cement;
  • silicone (colored, transparent...)
  • plastic which can be thermally recycled;
  • some kind of glue;
  • etc.
  • Gipsum / plaster is also a very readily available, non toxic material that's often used when crafting with children. Mix the dry gipsum with glue instead of plain water for added durability. – Elmy May 29 at 11:17
  • Wow! It never occurred to me to mig glue with gypsum. What kind of glue? Add the glue to the already wet gypsum, or dry? When I mentioned "some kind of cement", I also had gypsum in mind. – virolino May 29 at 12:13
  • The common paper / craft / white glue is ideal. The amount of glue to add depends on how strong you want the cast to become, how much water is in the glue to begin with and what material your mold is made off (you don't want the cast to stick in the mold). 50/50 glue and water yields a pretty stong result that doesn't crumble at the slightest provocation. Be aware that the cast can become tacky in high humidity due to the glue. – Elmy May 29 at 14:09
  • @Elmy, wow, I never thought that resin can really made from 50% of white glue + 50% of water! Amazing! – user275517 May 30 at 1:02
  • 1
    @user275517 Sorry, but you misunderstood. Gypsum is a material that can be used instead of resin, but (depending on the quality) it can be brittle. Adding some glue to the gypsum gives it more strength. You cannot make resin from water and glue. – Elmy May 30 at 5:37

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