Frequently Asked Questions

  • Where does a home or building need to be sealed, and why?

    A home or building needs to be sealed at its interior and exterior joints in order to prevent air and water infiltration.

    Internally, special attention should be given to seal joints in the kitchen and bathrooms of a home or building. The junctures of sinks and counters, bathtubs and walls and baseboards and walls, and the perimeters of faucets and window frames should all be sealed.

    Externally, door and window frames, skylights, chimneys, garage doors, outdoor faucets and roof junctures should all be sealed.

    Applying a sealant is a preventive measure. Even the most carefully constructed homes and buildings have gaps that need to be sealed in order to reduce air and water infiltration. Air infiltration increases drafts and heat loss, while water infiltration deteriorates building materials and can lead to expensive repairs. Mulco® products help seal out harsh weather and drafts for increased comfort, energy savings and peace of mind.


  • What is the difference between water-, solvent- and chemical-based sealants?

    The main differences in the three types of sealants are the ingredients used in the diluents. Diluents are the liquid ingredients in a sealant that are added to make products more fluid and easier to apply. When the diluents evaporate, or dry, an elastic, adhesive paste is left. This is your sealant.

    Water-based sealants contain water diluents in the product composition. They are also referred to as latex sealants or caulk. Water-based sealants are easy to use, affordable and paintable. They can be applied indoors and outdoors to a wide range of surfaces, including wood, ceramics, gypsum, masonry and glass. They can also be applied to damp surfaces.

    Solvent-based sealants utilize solvents as diluents. These solvents may include mineral spirits, toluene or xylene. They are mainly used outdoors and are best used with masonry, wood, bare metal and galvanized steel. Certain Mulco® solvent-based sealants have the benefit of being applicable to damp surfaces.

    Chemical-based sealants are composed of silicone, polyurethane or polysulphur diluents. They are also called silicone sealants. Chemical-based sealants must be applied to dry surfaces. They are preferred for their increased flexibility, long shelf life and ability to endure extreme temperatures. They are best utilized when sealing glass, fiberglass, bare metal, ceramics and wood.

  • How do I prepare the surface before applying a Mulco® product?

    If you are applying a Mulco sealant to a new, clean surface, you will have to do very little to prepare the surface other than wiping it down with a fresh, damp towel or sponge to remove dirt, dust and other particles. If you are applying a Mulco sealant to an area that has been previously painted or sealed, you will first have to clean and strip the surface. Otherwise, the old caulk, dirt, paint and oil will prevent the sealant from adhering correctly.

    1. Clean the Surface
    Cleaning should be done before removing old sealant to avoid water infiltration in the gap. The majority of surfaces can simply be cleaned with trisodium phosphate (TSP), isopropyl alcohol or a bleach mixture. While chemical cleaning solvents are available to help clean surfaces, they can adversely affect the finish of the surface because they are so aggressive.

    If you choose to use a chemical cleaning solvent, read and abide by all the safety guidlines recommended by the manufacturer.

    TSP Method: Follow the safety instructions and mix recommendations on the label. Spray the solution on the surface or juncture, and allow it to stand for a few minutes (without letting it dry). Rinse with clear water, and dry the surface with a clean towel.

    Isopropyl Alcohol Method: Pour a small amount of isopropyl alcohol on a clean cotton ball or towel, depending on the size of the surface. Rub the alcohol into the stripped juncture. This will collect any residual debris and clean the area. You can also pour isopropyl alcohol into a clean spray bottle. Spray the alcohol onto the surface or juncture and then wipe it down with a fresh towel.

    Bleach Method: Using bleach has the benefit of killing mold and mildew before you apply the new sealant. This is especially helpful in bathrooms. Mix a ratio of 1 part bleach with 3 parts warm water in a bucket. Use a sponge or clean towel to apply the bleach mixture to the area.

    2. Strip the Surface
    Stripping the surface means removing old layers of paint, varnish and sealant. There are several methods you can use to strip the surface: using good, old-fashioned elbow grease, applying a chemical stripper/remover or using a heat gun. While nearly all sealants can be removed manually, some people find using the chemical or heat method easier when removing solvent- and chemical-based sealants.

    Please note that silicone- and urethane-based sealants can leave a residue that can only be removed with a specialized chemical stripper. If you use another method to remove a silicone- or urethane-based sealant, you must replace it with the same type of sealant because the residue will prevent other types of sealants from adhering to the surface.

    Manual Method
    The manual method is recommended when removing paint or sealant that has been previously applied to the surface. We recommend wearing medium-duty leather gloves to protect your hands during this process.

    When removing old sealant: Remove as much caulk as possible by manually scraping it out of the juncture. Working slowly, slide a sharp utility knife or razor blade on either side of the existing seal. A damp sponge will help loosen the old product. Use a putty knife or razor blade-style scraper to scour the sealant out of the joint, pushing away from you. Be careful not to scratch the surrounding surface.

    When removing old paint: Depending on the surface, you can use a combination of a putty knife and wire brush to scrape off the paint. Use a damp sponge or towel to wipe up loose paint flecks.

    Once the majority of the paint or caulk is removed, you may use medium- to fine-grade sandpaper or a non-metallic abrasive pad to remove the remainder of the old product.

    Chemical Method
    Chemical strippers/removers are used to remove old coats of paint, stain, varnish and shellac from concrete, wood, metal, masonry and glass. Chemical strippers/removers are very caustic and require the use of safety goggles and a respirator.

    If you choose to use a chemical stripper/remover, it is absolutely imperative that you read and abide by all the safety guidelines recommended by the manufacturer.

    Heat Gun Method
    A heat gun is useful in removing multiple layers of paint or very hard sealants. The heat emitted from the gun softens the paint or sealant, causing it to bubble up so that you can easily remove it with a putty knife.

    Because heat guns often reach temperatures hot enough to vapourize paint compounds, avoid using a heat gun on paints containing lead, cadmium or other volatile, toxic chemicals.

    If you choose to use a heat gun, follow the manufacturer’s directions on proper usage.

    If you choose to use a chemical cleaning solvent, read and abide by all the safety guidelines recommended by the manufacturer.

    Household Cleaner Method: Spray your chosen household cleaner on the stripped surface or juncture, always following the manufacturer’s recommendations. Wipe the cleaner off the surface with a clean towel.

    You can also pour the bleach mixture into a clean spray bottle. Spray it on the surface or juncture and then wipe it down with a fresh towel. If there is heavy mold or mildew in the area, spray the area and allow it to work for 5-10 minutes before wiping it off.

    No matter which method you choose, ensure that the surface is completely dry before applying the new sealant. A dry surface will enable the sealant to adhere correctly.

  • At what temperature should I apply the sealant?

    When applying sealants, there is a temperature sweet spot for water- and solvent-based products. For best results, it is recommended to apply these products in an environment between 15° C and 30° C (59° F and 86° F).

    Be sure to take this into consideration before starting your next project. Please check the Mulco® Elastomer Sealant Characteristic Chart for product-specific recommended temperatures.

  • What is the proper way to apply Mulco® products?

    Other than temperature, the two most important factors in sealant application are joint shape and joint width.

    The “joint” refers to the sealant in its applied form. Most sealants, other than silicon, should be applied in a convex shape (meaning domed or curved outward) so that when it dries, it will form a flat, smooth surface. The sealant should always be applied so that it exceeds the width of the joint being sealed by at least 3 mm. (1/8 inch) on each side.

    Increase the width of the joint if:

    • You are sealing a surface that has already been covered in sealant
    • You need to hide defects in materials
    • The gap between materials is wider than 3 mm. (1/8 inch)

    First, cut the tip of the sealant nozzle off at a 90-degree angle with a utility knife, making it a little thinner than the required joint width. Completely break the thin aluminum membrane that separates the sealant from the nozzle. Insert the cartridge into a sealant gun. You are now ready to seal a juncture.

    Hold the gun at a 45-degree angle in the juncture and apply steady, even pressure to the gun’s handle. Pull the gun toward you while pushing the bead of sealant into the gap in one continuous movement.

    It is important to apply the sealant evenly. If there is too much pressure, the joint will be formed irregularly. If there is not enough pressure, the joint will not completely adhere to the surface.

  • How can I properly dispose of leftover sealant or caulks?

    There are three R’s to remember when dealing with leftover sealants and caulk. Reduce the amount of leftover sealant by purchasing only the amount needed for the job. When possible, reuse your extra sealant by giving it to a neighbor, friend or charitable organization in its original, labeled container. Retire water- and chemical-based sealants by emptying the cartridges onto an old newspaper.

    Allow the leftover sealant to dry out in a well-ventilated area, away from children and pets. After a few weeks, discard the remains into household trash. Check your local regulations before disposing of unused chemical-based sealants.

  • How should I store unused Mulco® products?

    If you are left with water-based sealant and want to keep it for future use, fasten an airtight cellophane cover over the tip. This will help preserve the sealant for a few months.

    If you are left with solvent-based sealant, fasten an airtight aluminum cover on the tip. This will help preserve the sealant for about two days. Force out a few inches of sealant before reuse.

    Always check the expiration date on your sealant before opening it.

  • How does Mulco® ensure the quality of its products?

    Mulco prioritizes quality of every phase of the manufacturing process.

    Unlike cheaper sealants, Mulco products are mixed in a vacuum to ensure a smooth finish. Then they are lab-tested to verify characteristics like consistency, colour and ease of application.

    When a product meets specifications, it is packaged using sophisticated equipment, and the amount of product in each container is checked before it is delivered.

  • How much sealant do I need for my project?

    The length of sealant you should be able to get out of a single cartridge (the "coverage rate") depends on: 1) the width of the juncture you need to seal, and 2) the thickness of the sealant bead, which you control by how high or low you cut the nozzle of the cartridge.

    See the chart below to determine the coverage rate for your specific project. Then divide the total length of the juncture you need to seal by the coverage rate you found using the chart. Round up to the next whole number. That is the number of cartridges you should buy.

  • What do the numbers and letters (batch codes) on Mulco® products mean?

    The seven-character code on a product package (including the six numbers and one letter) is called the batch code. The first number (6) indicates that the product was manufactured at the St-Hubert plant. The second number indicates the last digit of the manufacturing year (for example, 3 for 2013). The letter indicates the manufacturing month; the first fourteen letters of the alphabet; excluding G and I, correspond to the 12 months of the year. The last four digits indicate the batch number.

    You can use the batch code to figure out approximately how old a product is when storing sealants.