How to Match Silicone Sealant With Different Surface Materials?

Choosing the Right Silicone Sealant for Different Surfaces

Whether you’re tackling a DIY project at home, or are involved in professional construction work, chances are you will need to seal a joint, stop a leak, or combine two surfaces together. You will likely think to yourself, “I need sealant.” The first choice that comes to mind is likely a silicone sealant. It is waterproof, flexible, and sticks to a variety of surfaces. But not all silicone is created equally, and selecting the wrong silicone for your surface can cause a huge mess.

Think of selecting a sealant like a type of glue for a craft project. You wouldn't use school glue to repair a ceramic mug, right? Different materials mean different sealants. Some materials are porous, like wood and concrete, while others are glass and metals, which are non-porous and more slippery. Some materials expand and contract a lot and others very little. With 30 years of experience, Juhuan is one of the best manufacturers. Their silicone sealants are designed to meet the needs of specific surfaces. Different jobs require different formulations. Here, we will explain the materials and surfaces to help you select the right sealant every time for a lasting result.

The Big Picture: What Makes a Good Match?

Before we focus on something specific, let's discuss what the term "good match" means. Good match doesn't mean just having the sealant stick. It means forming a seal that is designed to last years and years, through sun, rain, heat, and cold. Two of the most important factors are adhesion and flexibility. Adhesion is how sticky the sealant is to the surface. Flexibility is how well the sealant is able to move with the materials as they expand and contract. When a sealant becomes too rigid and doesn't provide adequate movement, a mismatch occurs. When the materials move, the sealant will crack or pull away, and that seal is broken. The same sealant also may be too flexible, so that sealant would remain stuck, The same situation occurs if that sealant was too flexible to stick to a smooth surface. Understanding these basics will be an important first step in the decision-making process with the silicone sealant.

The Bond Between Glazing & Sealant

Sealing glass with silicone is where silicone and glass glazing can shine together. If you are glazing a facade, sealing an aquarium, or even sealing a window, a good quality neutral silicone is your best option. This is because silicone adhesive bonds well with glass.

For aquarium sealing, glass glazing, and glass sealing where the seal may be constantly wet, silicone should be used that is specifically rated for this purpose called “aquarium safe” silicone. This silicone is pure and does *not* have other additives that may be harmful to fish or may leach out over time. For window and facade glazing, a good quality neutral silicone will also create a clear, durable and weather-tight seal. Due to the high transparency, the silicone seal will also bond to glass creating a professional look to them with an almost imperceptible seal.

Wood: More Complicated as a Material

Wood is a different beast. Rather than being a solid and uniform substance, it is a porous material that is known to soak up moisture and, depending on humidity levels, will expand and contract. This also makes a tricky surface for sealants. You cannot simply go to the generic silicone. Using a standard, non-paintable silicone on wood is courting disaster. For one, it may not adhere to the bare wood fibers, and it may not really stick to the wood at all. Also, it will never be paintable, and that will be a major issue if you left the surface unfinished.

When sealing wood, you will want to use a sealant that is specifically made for surfaces that can be painted. Some silicones can be painted over. For some wood projects, especially interior trim and moldings, an acrylic or hybrid sealant that is water soluble and can be painted is a good option. However, if you require silicone's extreme flexibility and weather resistance for an outdoor wood joint, you will need to buy a good quality ''paintable silicone," and, of course, you should test for paint adhesion in an unnoticeable area first. For wood, surface preparation is crucial. It must be clean, dry, and free of dust and old finish.

Metal surfaces, like aluminum window frames, steel gutters, and copper flashing, are also common sites for sealants. Metal is non porous and can be slick, especially if it has a factory coating or if it is oily. Some metals can corrode when in contact with certain chemicals, and that can be a problem with some sealants.

This is where choosing the right silicone sealant is critical.

If you are looking for an effective sealant for use with metals, neutral cure silicone is typically the best option because it will not corrode, stain, or rust the metal and will adhere well to clean metal. Make sure to thoroughly degrease the metal, because silicone will not adhere properly to surfaces that are oily, greasy, or coated. When degreasing, use a solvent such as alcohol or acetone. If the metal surface will oxidize and is uncoated, do a quick wipe to remove any loosely adhered oxide dust. After making contact with a clean surface, a neutral cure silicone will maintain a durable, flexible, and strong bond with the metal.

Concrete, brick, stone, and mortar are materials that are strong, porous, and rough. Silicone sealants work well with these materials because they can penetrate pores and bond very effectively.Masonry surfaces can pose challenges when working such as being dirty, dusty, or wet. Use a wire brush to remove any large debris, and clean the surface thoroughly. The surface must be dry for the best bond. Most jobs are suited with a good, quality, all purposes silicone sealant. Additionally, a backer rod may be necessary for larger joints to support the sealant and allow for joint movement. The silicone's flexibility is a great advantage as it can accommodate small movements in the masonry and won't crack.

Compatibility Testing

Plastic is varied and it is one of the most problematic material categories. From rigid PVC and rigid polycarbonate to flexible plastics and composites, the variety is endless. The simple fact is that certain sealants can react with certain plastics and soften, crack, or discolor them. This is known as plasticizer migration or chemical incompatibility.

Neutral cure silicone sealants are generally a safe and strong choice for standard plastics like polycarbonate (used in skylights and greenhouses) and PVC (used in pipes and windows). Be sure to read the manufacturer's guidelines before applying. If dealing with other types of plastics, you can prevent potential mistakes by applying a small amount in an inconspicuous spot before fully sealing the joint. Give the sealant a day or two to cure and check for any adverse reactions. Doing this in advance can avoid having your project ruined. Most good quality manufacturers design their silicone to be compatible with most common construction plastics.

Curing and cleanup

Two more tips that apply to every surface are curing and cleaning up. As you are most likely already aware, cleanup and curing take time, and curing generally requires you to let the sealant sit undisturbed. Sealant typically takes from 24+ hours to fully cure, which means that during that time, the sealant needs to be undisturbed so that it can cure. If you need to clean up the area before the sealant skins, be sure to have the proper cleanup agents (e.g. mineral spirits, a silicone-specific cleaner) to smooth the seam and clean up any mistakes. Once silicone cures, it cannot be removed, so try to be as neat as possible.

It may seem small, but considering the surface material when choosing silicone sealant will give you a long-lasting professional finish. It's important to appreciate the movement potential of the sealant and how it will perform with the other materials in your build or repair as a manufactured extension of your construction. Selecting a sealant compatible with the surface will lead to a successful outcome in terms of time, cost, and frustration.