RTV Molding Compounds | McMaster-Carr

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19 Products

Quick-Set Casting Compounds

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. Use them to make your own prototypes, molds, and linings.

Casting Compounds

Silicone Rubber

Soft—Soft silicone rubber is more flexible and easier to peel off of molds than hard silicone rubber, especially when making complex shapes.

Hard— Hard silicone rubber holds its shape better than soft silicone rubber, so small ridges and channels are less likely to collapse or deform while making molds.

69° F Cure Temperature—Combine acrylic plastic or silicone rubber with a 69° cure temperature compounds in different ratios to adjust the consistency from thin to thick. Thin mixtures are easier to pour and better for filling small crevices.

70° F Cure Temperature—Silicone rubber with a 70° cure temperature compounds are a putty that you can mix with your hands and form into any shape. Press an object into these compounds to create a mold for casting duplicates. They do not shrink as they dry, so textures and other fine details are captured faithfully.

	Time to Demold, min.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Silicone Rubber







	Soft

	Durometer 27A	2	15	15	70	650	0%	Light Blue	Yes	4	0.2	0000000	000000


	Durometer 27A	2	15	15	70	650	0%	Light Blue	Yes	46	2.2	0000000	000000
	Durometer 30A	2	10	10	69	250	0%	Green	Yes	8	0.5	0000000	00000
	Durometer 30A	2	10	10	69	250	0%	Green	Yes	23	1.1	0000000	000000




			Hard

			Durometer 40A	2	15	15	70	600	0%	Green	Yes	4	0.2	0000000	00000


			Durometer 40A	2	15	15	70	600	0%	Green	Yes	46	2.2	0000000	000000
			Durometer 50A	2	10	10	69	250	0%	Light Blue	Yes	13	0.8	0000000	000000
			Durometer 50A	2	10	10	69	250	0%	Light Blue	Yes	32	1.75	0000000	000000

Casting Compounds with Dispensing Gun

Compounds with dispensing gun come ready to use—no mixing required—and won’t leave a mess.

Hard— Hard silicone rubber holds its shape better than soft silicone rubber, so small ridges and channels are less likely to collapse or deform while making molds.

Soft—Soft silicone rubber is more flexible and easier to peel off of molds than hard silicone rubber, especially when making complex shapes.

	Hardness	Time to Harden, min.	Time to Cure	Time to Demold	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Wt., lb.	Includes		Each
Silicone Rubber



	Soft	Durometer 30A	2	10 min.	10 min.	69	250	0%	Green	No	4	Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	0000000


	Soft Hard	Durometer 30A Durometer 55A	2	10 min. 6 min.	10 min. 6 min.	69	250	0%	Green Orange	No	4	Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	000000
	Hard	Durometer 55A	2	6 min.	6 min.	69	250	0%	Orange	No	4	15 Disposable Nozzles, 2 Snap-On Nozzles, Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	000000

Replacements for Casting Compounds

Nozzle Type	Pkg. Qty.		Pkg.
Angled	15	0000000	000000
Straight	15	0000000	00000

Color	Volume, cu. in.		Each
Green	3	0000000	000000
Orange	3	0000000	00000

Chemical-Resistant Casting Compounds

This silicone rubber 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 rubber, which easily demolds.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Silicone Rubber







	Hard

	Durometer 65A	120	24	16	78	400	0%	Blue	Yes	22	1	0000000	000000


	Durometer 65A	120	24	16	78	400	0%	Blue	Yes	242	11	0000000	000000

Long-Life Casting Compounds

Create rubber molds that retain their shape for decades—they won’t soften, degrade, or warp, so you can continue to replicate intricate parts. Because these compounds don’t shrink as they cure, they are more accurate and predictable than other compounds.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber







	Hard

	Durometer 45A	60	24	16	77	200	0%	Yellow	Yes	58	2.2	0000000	0000000

See-Through Casting Compounds

Create transparent molds to monitor fill levels, differentiate parts at a glance, and avoid damaging parts when cutting the mold away. These casting compounds are two parts that activate when mixed.

View our selection of release agents.

Silicone Rubber—Silicone rubber compounds handle higher temperatures than urethane rubber compounds—up to 570° F. Silicone rubber also cures faster than urethane rubber, 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 rubber compounds trap 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.

	Time to Demold	Cure Temp.	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Silicone Rubber







	Hard

	Durometer 40A	10	1.5 hr. 30 min.	1.5 hr. 30 min.	77° F 120° F	570	0%	Blue	Yes	57	2.2	0000000	0000000