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Creating a Marble Effect

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                                       © Smooth-On, Inc. (2005)
 

FAQ: How can I make castings that look like marble?

A: Creating a realistic cast marble effect is possible with Smooth-Cast 325 liquid plastic. Calcium carbonate (also known as “marble dust”) is mixed with SC 325 casting resin until the mixture is thick and creamy.  This mixture is then simultaneously cast with black pigmented  Smooth-Cast 325 to create the “veining” effect commonly found in marble.   Getting the effect you want will take practice and we offer the below as a step by step outline to get you started.

Products Needed:      A. Calcium Carbonate (moisture free)     

                                      B.  Smooth-Cast 325 Casting Resin    

                                      C. Liquid Color Pigment (black & white) 

A.  Calcium Carbonate – Calcium  Carbonate (marble dust) should be completely free of moisture.  Calcium Carbonate is available from many Smooth-On distributors.  Call our technical help line to find your nearest distributor.
 

B.  Casting Resin -  Smooth-Cast 325 Colormatch is recommended because it is “color neutral” and readily accepts powders and/or pigments. 
 

C.  Liquid Pigment - Adding a pigment to the resin/calcium carbonate mixture will give the final casting added definition and dimension.

Also required: Rubber Mold; Mold Release Agent; measuring and mixing containers; mixing paddles; Gram scale or triple beam balance for weighing components.

    Amount of resin, calcium carbonate and pigment required will vary depending on the desired effect.  You will have to experiment by varying the amounts of resin, calcium carbonate and pigment used in combination to attain an effect that suits your application.

For this example, we will use the following proportions:

     Part B of SC 325 Resin:  100 Parts              
Calcium Carbonate:  100 Parts
Part A of SC 325 Resin:  100 Parts              
So-Strong Pigment:   Black & White 1/2 Part Each

     Measuring can be done by volume.  Greater accuracy is achieved with a gram scale.

1.  Apply Release Agent to Rubber Mold** - If casting into a urethane rubber mold, prevent resin mixture from sticking to rubber mold with application of a spray mold release agent (Smooth-On Universal Mold Release™) into mold cavity and all surfaces that will contact the resin. Brush lightly and follow with second light mist coating.  Let dry for 20 minutes.

2.   Create Calcium Carbonate “Part B” Pre-Mix - mix calcium carbonate thoroughly with Part B of SC 325 (Blue Label).  Dispense 100 Parts of Part B into clean mixing container.  Add 100 Parts of calcium carbonate and mix thoroughly.  The consistency of the mixture will be very thick.

3.  Create White Pigmented ‘Part A’ Pre-Mix – Dispense 100 parts of Smooth-Cast 325

Part A into mixing container and add ½ part of white pigment.  Mix thoroughly. 

Decanting from Premixes  – From the pre-mixes created in steps 3 and 4, dispense equal amounts into separate measuring containers (Hint:  Only a small amount of each Pre-Mix is required –a small 2 ounce dixie cup of each is ideal.)  At this point you should have 4 pre-measured “Pre-Mix” containers:  1 large and 1 two ounce container of both the ‘Part A’ and ‘Part B’ Pre-Mix.

5.    Create A Black Color Concentrate For Veins – Combine the small ‘Part A’ Pre-Mix with the small ‘Part B’ Pre-Mix and add the ½ part of So-Strong Black pigment.  Mix thoroughly and set aside for use later.  (After mixing the concentrate you will have about 3 minutes to work before it begins to cure).

6.   Combine the remaining large containers of Part A (from Step 3) & Part B (from Step 2) and mix thoroughly.

Add Black Color Concentrate To Create Veining – Apply the Black Concentrate (from Step 5) to a tongue depressor and dip this into the large container of material created in Step 6.  Slowly swirl the tongue depressor to create color variation.  Several applications of the Black Concentrate may be necessary to obtain desired color effect. 

8.   Pour Mixture into Mold – Pour the mixture from Step 7 into your mold.  The black swirls in the mix will form a natural “veining” effect as you pour.  As we said earlier, achieving an acceptable veining effect may take some practice.

9.  Allow Casting To Cure Before Demolding - Remember: the resin/calcium carbonate mixture or filled resin will take longer to harden than unfilled resin.  Cure time depends on size of casting, mold configuration, amount of fillers used, etc.  Generally 30 to 40 minutes is a sufficient amount of time.  Applying mild heat will accelerate cure time. Let cool to room temperature.

10. Demold the casting from mold - Lightly polish casting with a wax until the desired luster is attained. 

    ** Use only a release agent specifically made for mold making and casting such as Universal Mold Release™ or Mann Ease Release 2300™ (both available from Smooth-On and its distributors).