McMaster-Carr

These compounds make transparent molds, so you can monitor the fill level, identify molds after casting, and avoid damaging parts when cutting the mold away. All are two-part compounds; mix together to activate.

Urethane compounds create hard molds, which are good for delicate and intricate shapes because the small contours won't deform or collapse when the material is poured in. Although not necessary, curing urethane molds inside a vacuum chamber improves their clarity. By removing trapped air bubbles, the chamber prevents the finished mold from looking speckled.

Silicone compounds handle much higher temperatures than urethane compounds—up to 570° F. Silicone also cures faster than urethane, and it won't shrink as it cures, which means you won't need to guess at the final size of your mold. Because silicone compounds trap a lot of air bubbles when mixed, they must be cured inside a vacuum chamber. The chamber removes the trapped air bubbles, strengthens the mold, and improves its clarity.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Hard
Durometer 80A	6 min.	144 hrs. @ 77° F	2 hrs. @ 77° F	180°	5%	Clear	Yes	25	1	0000000	000000
Durometer 75D	6 min.	144 hrs. @ 77° F	2 hrs. @ 77° F	180°	5%	Clear	Yes	25	1	0000000	00000
Silicone Rubber
Firm
Durometer 40A	15 min.	1.5 hrs. @ 77° F, 30 min. @ 120° F	1.5 hrs. @ 77° F, 30 min. @ 120° F	570°	0%	Blue	Yes	57	2.2	0000000	00000

Casting Compounds

Capture intricate details when creating prototypes, molds, and linings with these easy-to-mix two-part compounds. This urethane is water and abrasion resistant.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Soft
Durometer 20A	15 min.	168 hrs.	5 hrs.	77°	180°	1.5%	Black	Yes	25	1	0000000	000000
Durometer 20A	15 min.	168 hrs.	5 hrs.	77°	180°	1.5%	Black	Yes	250	10	0000000	000000
Firm
Durometer 40A	15 min.	168 hrs.	5 hrs.	77°	180°	1.5%	Black	Yes	25	1	0000000	00000
Durometer 40A	15 min.	168 hrs.	5 hrs.	77°	180°	1.5%	Black	Yes	250	10	0000000	000000
Durometer 60A	15 min.	168 hrs.	2 hrs.	77°	180°	0.5%	Black	Yes	25	1	0000000	00000
Durometer 60A	15 min.	168 hrs.	2 hrs.	77°	180°	0.5%	Black	Yes	250	10	0000000	000000
Hard
Durometer 80A	15 min.	168 hrs.	3 hrs.	77°	180°	1.5%	Black	Yes	6	1/4	0000000	00000
Durometer 80A	15 min.	168 hrs.	3 hrs.	77°	180°	1.5%	Black	Yes	25	1	0000000	00000
Durometer 80A	15 min.	168 hrs.	3 hrs.	77°	180°	1.5%	Black	Yes	250	10	0000000	000000
Durometer 94A	15 min.	168 hrs.	2 hrs.	77°	180°	1.5%	Black	Yes	25	1	0000000	00000
Durometer 94A	15 min.	168 hrs.	2 hrs.	77°	180°	1.5%	Black	Yes	250	10	0000000	000000
Durometer 60D	15 min.	168 hrs.	2 hrs.	77°	180°	1.5%	Black	Yes	25	1	0000000	00000
Durometer 60D	15 min.	168 hrs.	2 hrs.	77°	180°	1.5%	Black	Yes	250	10	0000000	000000
Durometer 85D	5 min.	2 hrs.	1.5 hrs.	77°	180°	1.5%	Blue-Green	Yes	80	5	000000	00000
Durometer 85D	5 min.	2 hrs.	1.5 hrs.	77°	180°	1.5%	Blue-Green	Yes	320	20	000000	000000

Machinable Casting Compounds

After these compounds cure, they're tough enough to be machined. They are easy-to-mix two-part compounds that capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents. View additional information about the hardness of these materials.

Epoxy
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Hard
Durometer 86D	50 min.	18 hrs.	18 hrs.	75°	130°	1.5%	Gray	Yes	40	2.7	00000000	000000
Aluminum-Filled Urethane
Hard
Durometer 83D	6 min.	18 hrs.	2 hrs.	75°	175°	1.5%	Gray	Yes	83	5	00000000	00000
Durometer 83D	6 min.	18 hrs.	2 hrs.	75°	175°	1.5%	Gray	Yes	334	20	00000000	000000

Fast-Setting Casting Compounds

Acrylic

Silicone

Create detailed rubber shapes that are ready to use in fifteen minutes or less. Unlike traditional casting compounds, which can take up to 24 hours to set, these compounds harden after two minutes, and can be removed from molds within fifteen. Mix two parts together to make your own prototypes, molds, and linings.

Combine acrylic compounds in different ratios to adjust the consistency from thin to thick. Thin mixtures are easier to pour and better for filling small crevices. Thick mixtures will shrink less as they dry.

Silicone compounds are a putty that you can mix with your hands and press or form into any shape. They do not shrink as they dry, so textures and other fine details are captured faithfully. Soft silicone is easier to remove from molds than firm silicone, especially when making complex shapes. Firm silicone holds its shape better than soft silicone, so small ridges and channels are less likely to deform or collapse over time.

View our selection of release agents. View additional information about the hardness of these materials.

Acrylic
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Hard
Durometer 85D	2 min.	11 min.	11 min.	69°	350°	1.5%	Light Blue	Yes	20	1	0000000	0000000
Durometer 85D	2 min.	11 min.	11 min.	69°	350°	1.5%	Light Blue	Yes	62	3	0000000	000000
Silicone
Soft
Durometer 27A	2 min.	15 min.	15 min.	70°	650°	0%	Light Blue	Yes	4	0.2	0000000	00000
Durometer 27A	2 min.	15 min.	15 min.	70°	650°	0%	Light Blue	Yes	46	2.2	0000000	00000
Firm
Durometer 40A	2 min.	15 min.	15 min.	70°	600°	0%	Green	Yes	4	0.2	0000000	00000
Durometer 40A	2 min.	15 min.	15 min.	70°	600°	0%	Green	Yes	46	2.2	0000000	00000

Fine-Detail Casting Compounds

Replicate even the most complex details when creating prototypes, molds, and linings. This easy-to-mix two-part compound flows smoothly into crevices.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Hard
Durometer 83D	8 min.	168 hrs.	2 hrs.	75°	135°	1.5%	White	Yes	94	3.6	00000000	000000
Durometer 83D	8 min.	168 hrs.	2 hrs.	75°	135°	1.5%	White	Yes	374	14.4	00000000	000000

Easy-to-Work Casting Compounds

Combine the liquid components to form a putty that can be molded into or around any shape. Use these compounds to capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Firm
Durometer 60A	15 min.	168 hrs.	3 hrs.	75°	180°	1.5%	Black	Yes	25	1	0000000	000000
Durometer 60A	15 min.	168 hrs.	3 hrs.	75°	180°	1.5%	Black	Yes	100	4	0000000	00000
Hard
Durometer 85A	15 min.	168 hrs.	3 hrs.	75°	180°	1.5%	Black	Yes	25	1	0000000	00000
Durometer 85A	15 min.	168 hrs.	3 hrs.	75°	180°	1.5%	Black	Yes	100	4	0000000	00000

High-Temperature Casting Compounds

Capture intricate details when creating prototypes, molds, and linings with these easy-to-mix compounds.

Alumina is high strength.

High-purity alumina resists shrinking in casts, has a low level of contamination, and is a strong electrical insulator. It’s often used for constructing furnaces and handling liquid metal.

Silicon carbide has a high heat transfer rate, making it ideal for use in metal casting molds. It has the added benefit of excellent erosion and oxidation resistance.

Silica withstands rapid changes in temperature without cracking and has a low rate of thermal expansion.

Zirconium oxide is often used in metal handling applications. In addition to its high temperature resistance, it’s also chemical resistant.

View our selection of release agents.

Alumina
Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
20 min.	24 hrs.	24 hrs.	77°	3000°	1.5%	White	Yes	38	4	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	3000°	1.5%	White	Yes	96	10	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	3000°	1.5%	White	Yes	480	50	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	3000°	1.5%	White	Yes	960	100	0000000	000000
High-Purity Alumina
25 min.	24 hrs.	24 hrs.	77°	3200°	1.5%	White	Yes	98	10	0000000	000000
25 min.	24 hrs.	24 hrs.	77°	3200°	1.5%	White	Yes	490	50	0000000	000000
Silicon Carbide
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	Black	Yes	47	4	0000000	00000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	Black	Yes	119	10	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	Black	Yes	595	50	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	Black	Yes	1,190	100	000000	000000
Silica
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	White	Yes	62	4	0000000	00000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	White	Yes	155	10	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	White	Yes	785	50	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	2700°	1.5%	White	Yes	1,570	100	0000000	000000
Zirconium Oxide
20 min.	24 hrs.	24 hrs.	77°	4000°	1.5%	Tan	Yes	27	4	0000000	00000
20 min.	24 hrs.	24 hrs.	77°	4000°	1.5%	Tan	Yes	69	10	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	4000°	1.5%	Tan	Yes	340	50	0000000	000000
20 min.	24 hrs.	24 hrs.	77°	4000°	1.5%	Tan	Yes	690	100	0000000	00000000

Chemical-Resistant Casting Compounds

This silicone compound offers good resistance to acids, oils and salt water. Use it to capture intricate details when creating prototypes, molds, and linings with this easy-to-mix two-part compound. It is a durable and tear-resistant silicone, which easily demolds.

View our selection of release agents. View additional information about the hardness of these materials.

Silicone
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Firm
Durometer 65A	120 min.	24 hrs.	16 hrs.	78°	400°	1.5%	Blue	Yes	22	1	0000000	000000
Durometer 65A	120 min.	24 hrs.	16 hrs.	78°	400°	1.5%	Blue	Yes	242	11	0000000	000000

Food Industry Casting Compounds

These food-grade compounds comply with FDA 21 CFR. They are easy-to-mix two-part compounds that capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Specifications Met	Volume, cu. in.	Weight, lbs.		Each
Firm
Durometer 60A	8 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	000000
Durometer 60A	8 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000
Hard
Durometer 78A	4 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
Durometer 78A	4 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000
Durometer 88A	4 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
Durometer 88A	4 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000
Durometer 75D	5 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
Durometer 75D	5 min.	12 hrs.	2 hrs.	120°	180°	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000

Long-Life Casting Compounds

Create rubber molds that keep their shape and strength for decades. Formulated to last longer than other casting compounds, these compounds produce molds that won’t soften and degrade so you can cast the same intricate part every time. Since these are two-part compounds, they must be mixed together to activate. Unlike other casting compounds, they won’t shrink during curing for accurate, predictable results.

View our selection of release agents. View additional information about the hardness of these materials.

Urethane
Hardness	Time to Harden	Time to Cure	Time to Demold	Cure Temperature, °F	Max. Temperature, °F	Shrinkage	Color	Mixing Required	Volume, cu. in.	Weight, lbs.		Each
Firm
Durometer 45A	60 min.	24 hrs.	16 hrs.	77°	200°	0%	Yellow	Yes	58	2.2	0000000	000000

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