filling silicone sealing

Silicone rubbers are man-made elastomers or materials that have both liquid and rubber properties. They start as liquids of varying viscosities, and then cure to a solid form.

There are four main types of silicone rubber:

  • Room Temperature Vulcanizing, or RTV
  • High-Temperature Vulcanizing, or HTV
  • High-Consistency Rubber, or HCR
  • Liquid Silicone Rubber, or LSR

Each of these materials has a different formulation that gives it its unique properties. The amount of flexibility, adhesion, durability and elasticity varies for each of them, making them appropriate for different uses.

RTV silicone is one of the most common silicone rubbers used in industrial and personal applications. We’ll dig a bit deeper into what makes it so easy to use, some different applications and then look at some practical considerations.

 RTV silicone

RTV silicone is a versatile compound that can be used in many ways, in a variety of  industries. This versatility makes RTV silicone convenient to use. You see RTV silicone used in construction and automotive maintenance, as well as theatre and at-home projects.

Using RTV silicone is convenient

  • It can be found in a one-step formula that requires no mixing.
  • It has a long shelf-life.
  • RTV silicone comes in a range of thicknesses (viscosities), so it can be applied to surfaces by spraying, brushing or pouring.
  • It doesn't shrink as it dries.
  • The final product is highly chemical and temperature resistant.
  • RTV silicone remains flexible after it cures.
  • It captures fine details in casting and molding.
  • The formulas don't require a releasing agent.

RTV silicone has many uses


Sealers block water or other fluids from passing through joints and openings of material. RTV is a good barrier to water and won't distort over time. Additionally, RTV silicone easily bonds to common household materials, such as wood and tile.

A bead of silicone sealant is applied around your home's windows to keep water from entering the house from outside. It's applied in the bathroom around sinks, showers and tubs, as well as the toilet. In the kitchen, it’s used similarly around sinks and faucets.

RTV can also be used to seal areas of your vehicle, such as a vinyl top, and around windshields, door frames and roof seams.


Gaskets are a specific kind of seal used between two surfaces that are under pressure. They're used as a barrier to sound, liquid or vibration, and sometimes a combination of all three.

RTV makes a good gasket material because most chemicals won't damage it, and it flexes under pressure. Its shape is also really forgiving; it can be used to mate surfaces that aren't perfectly smooth.

Most people are familiar with the various gaskets located in a vehicle’s engine, but gaskets are used anytime you need a bit of cushion when two surfaces are stuck together.


The qualities that make RTV a good material for gaskets also make it a good material for casting and molding. It can be easily poured or brushed around objects and will catch fine details; also, the final product is flexible enough to stretch without damage. Molds and casts retain their shape for a long while. Additionally, they require no release agent or extra post-production clean-up.

RTV silicone can be used to cast wax, polyester resins and gypsum. It's also suitable for metals such as tin, zinc and pewter that have low melting points.

As a brush-on, the curing times between layers are faster than urethanes, but slower than latex.

 hot glue gun crafts


RTV is only mildly adhesive so that it can be easily removed from most items. In crafts, it's used to mock-up models, create stencils, scrapbooking and making soap or figurines. Since it doesn't shrink and dries clear, using RTV won't alter the overall appearance of your project.

Some practical considerations when using RTV silicone

  • Make sure your sealant/adhesive matches your application. Read the packaging thoroughly before beginning any project.
  • Knowing which glue gun to use is just as important as knowing which adhesive. You'll need one that fits your specific cartridge. If you're unsure, feel free to contact us for assistance.
  • You don't need a lot of RTV silicone to get the job done, especially when creating a gasket. Extra material will seep onto unintended areas.
  • Make sure to wait the entire cure time before using your project. RTV cures by reacting with water in the air so ambient humidity will affect cure time. It will take longer to cure in dry locations; on the other hand; it will cure quickly in very humid locations.
  • Don't use silicone on a galvanized surface.
  • Properly prepare your surfaces, preferably within 24 hours of applying the RTV silicone. You want to remove any debris and residues that will interfere with adhesion, curing or curing. For materials such as glass, plastic and metal you can wipe the surfaces with mineral spirits.
  • Refrain from using soap products to prep your surfaces. Soaps leave a residue that interferes with the surfaces sticking together.
  • RTV starts curing as soon as air touches it, but different formulations will have different tooling times. Tooling time is the amount of time you have before it starts to skin over. During this time, the sealant/adhesive can be smoothed and formed.
  • Store unused sealant/adhesive by removing air from the container, and then keeping the cartridge in a cool, dry area. Often, this entails pushing the sealant/adhesive material to the tip of the cartridge, and then replacing the cap. Any air in the cartridge will cause the material to harden in the container.


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