Simple Resin and Plastic Casting

Lesson 2: Simple Resin and Plastic Casting

Resin Safety:

Almost all of the resins and plastics available contain toxic chemicals. Pay attention to the warnings and read the MSDS sheets. To prevent any health issues, use common sense and follow the following:

• ALWAYS wear your face mask and gloves.
• ALWAYS use resins under ventilation.
• NEVER eat or drink where you are using resin.
• NEVER work with resin on any hot surface.

Preparation:

Make sure that you have a clean counter area to work on. Do not work on countertops that have soldering equipment or work in the designated enamelling area.

Lay down parchment paper to protect the countertops on the areas you will be using. You can secure the parchment paper with masking tape if needed. You must use parchment paper, freezer paper, tin foil or wax paper. Magazine pages and regular paper or paper towel will absorb the resin and glue themselves to the counter.

Make sure that the ventilation is on.

Preparing the Piece/Mold:

If you are pouring resin/plastic into a piece of jewelry:

Make sure that the piece is finished with the exception of the resin. All polishing should be done, all soldering should be done, all stone setting should be done, and all patination should be done. Pouring the resin should be the last step.

Test out the resin you are using to make sure that you can get the color and effect that you want in the piece before doing the actual pour. This will save you time if the “clear” resin you had planned to use isn’t.

Make sure that your piece is securely supported. If you are trying to create a level surface, make sure to level your piece prior to pouring.

If you are using a slow-drying resin, your supports much be stable enough to move the piece from the countertop to the drying area.

If you are pouring resin/plastic into a mold:

Coat the interior surfaces (those that will contact the resin) with a mold release spray. Make sure that the spray you use is compatible with your mold material!! Some sprays are only for silicone rubber, some only for polyurethane! Smooth-On’s Universal Mold Release is a good one to use.

Clamp your mold together (if a 2-part)

Situate and support your mold so that it is easy to pour into. Make sure that the openings are reachable and unobstructed.

Again, make sure if you are using a slow curing resin, that you can move your mold to the curing area easily.

Simple Resin/Plastic Casting:

Each type of resin/plastic should come with the mixing proportions listed on the packaging or instruction sheet.

The steps to mix and pour don’t vary much from type to type.

If you are using one of the quicker setting resins or plastics, and you have a specially mixed color pigment, make that up and keep it in a small container at the ready.

For best results, mix in a plastic cup with graduated markings on the side.

Pour Part A or the Resin into the cup. Remember to only pour half of the total amount you will be using! You still have the second part to go.

-If using a quicker setting resin, put in the color now.

Pour Part B or the Hardener into the cup.

-If using a slower setting resin add the color now.

Stir completely with a popsicle stick. Make sure to scrape the edges of the cup and the bottom of the cup.

With some of the resins, you can see the 2 parts mixing together- the resin looks slightly cloudy or streaky and then clears up when completely mixed.  This is easier to see without color in the resin.

Pour the resin into/onto the piece. Pour in a steady stream.

Let cure.

Coloring:

You can use many different things to color resin- each will bring a unique look to the piece. Try several and keep a log of what you used with each sample.

A quick way to make samples is to dab a bit of resin (if using Colores brand, use the thick hardener) onto a piece of parchment paper. When the resin cures it will pop right off giving you a nice small sample.

For the clearest and truest color, use straight liquid pigments. Polytek’s brand is PolyColor, Michael’s carries Castin’ Craft, and Smooth-On has their SoStrong pigments.

The pigments can be blended to achieve mixed colors (red+ blue= purple). The pigments take a long time to dry out, so if you keep them in a sealed container they will last months. The pigments are also very strong. It doesn’t take a lot of pigment to get a deep color. One drop of red pigment into an ounce gives you a deep blood red.

When adding color, start with just a bit and then make the resin darker if needed. It is very hard to lighten the color.

You can use ceramic paints to color the resin, but with these there is a limit as to how much paint you can add. I recommend the pigments over the paints.

You can also use powdered color- powdered tempera, ground up chalk pastels, powdered dyes, powdered pigments- to color  the resin. Depending on the fineness of the material grains some powders will give the resin a grainier appearance. 

Tips and Tricks:

• Measure, measure, measure. The cup should be resting level on the countertop when you are measuring. Get down to the cup level so that you can read the amount accurately. 90% of resin problems are caused by poor measuring or mixing!
• When stirring the parts together, keep the popsicle stick in the resin- pulling it in and out introduces more air into the resin.
• Stir slowly and thoroughly- keep bubbles to a minimum.
• Use the flexibility of the cups to help control your pour- bend the cups to create a narrower spout for more precise application.
• If you leave the popsicle stick in the cup after pouring, once the resin cures you can pop out the cured resin and the stick, letting you reuse the cup over and over.
• If you are worried about the resin not being completely mixed, you can transfer the resin from one mixing cup to another after putting both parts in. This ensures a complete mix.
• If using the Polytek clear resin, you will be able to tell whether the proportions are correct because if they are not, it turns opaque.
• When pouring into a mold- pour slowly and tap the mold on the counter to help release air bubbles. For delicate molds, you may also want to gently peel the mold open a bit as well in addition to cutting lots of air vents.
• For covering or giving a clear topcoat to a photo or some other image, I recommend Envirotex resin. This resin is reasonably bubble-free when mixed correctly and can be heat gunned to achieve better clarity. It is slow-drying which is better for clear coats as it gives you time to correct any mistakes as you go.
• With slow-curing resins, you can wave a heat gun or hairdryer gently over the piece to help bring any trapped air bubbles to the surface. Once on the surface you can prick them with a pin to pop.
• If you have air bubbles in your piece after it cures, you can inject a small amount of resin into the bubble with a syringe.
• For pouring into molds or intricate parts, I recommend the polyurethane plastic (Polytek or Smooth-On) over the epoxy resins. The polyurethane plastics I have found are also better about debubbling themselves than the epoxy is.
• Several people have reported skin allergies/rash/sensitivity with the Smooth On crystal clear plastic. Many of the optically (or water) clear plastics have very large warnings about using them. Pay attention to these!! Sensitivity is greatest when in liquid form and during finishing. Once the product has cured and sealed, there isn’t as large of an issue. As there is no way to tell whether you have this sensitivity until you use the product, please be careful and make extra sure to follow all of the safety precautions. If you do develop a rash, stop using the product.