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How to Apply Silicone Sealant: A Step-by-Step Guide

by Georgia Nunn 13 May 2024
How to Apply Silicone Sealant: A Step-by-Step Guide

Silicone sealant is a form of adhesive, used to create a water and airtight seal at the joint between two surfaces. Typically, it has a liquid, gel-like consistency when first applied. This then dries to a more sturdy, flexible rubber-like texture after being allowed to cure under suitable humidity and temperature conditions. Once cured, silicone sealants achieve the consistency of a flexible silicone rubber-like material.

It is commonly sold in two different forms, a squeezy tube used for manual application by hand or a more rigid cartridge. The cartridge is to be inserted into a sealant gun, which can help to produce a neater finish. 

Silicone sealants are often chosen over other adhesives and sealants due to their prolonged durability and improved flexibility. Once they are fully cured, they provide a hard-wearing elastic bond that both holds its shape and joins areas that are frequently used and exposed to moisture.

Prepare your surface

Prior to sealing, you will need to remove any previous silicone from all surfaces (if any remains). You will then want to ensure that the area surrounding the sealant is clean, dry and free from any dust, grease and any other contaminants that may affect adhesion.

If the surface is non-porous, it will need to be degreased using white spirit or a non-oily solvent and then washed clean , and left to dry.

How to Apply the Silicone Sealant

Using a utility knife, cut the end of the silicone cartridge seal and screw on the nozzle. The nozzle should then be cut at a 45° angle. The cone shape of the nozzle will allow you to adjust the width of the opening.

Once this has been cut:

  1. Place the silicone cartridge in to the sealant gun
  2. Squeeze the sealant gun handle, pushing the silicone until it comes to the end of the nozzle. Silicone beads should be applied by dragging the gun backwards, towards yourself.
  3. Start in a corner and drag the sealant gun backwards over the surface at a 45° angle while squeezing the sealant gun handle.

The best working position to hold the sealant gun is at 45°,  pulling the gun backwards, towards yourself. To ensure the sealant is applied neatly you will need to find the right working speed. 

  • If you move too slowly, you’ll get a bumpy, irregular surface, using too much and wasting the sealant unnecessarily. 
  • If you move too quickly, you will not fill the gaps properly, risking that the seal will not be water-tight, lessening the life of the sealant.

Smooth the Surface

To get a smooth finish on your sealant

  • Wet your finger with some soapy water and then wipe it along the silicone bead, smoothing out the seam. The soap will prevent the silicone sealant from sticking to your finger.
  • You can also use a plastic or rubber silicone smoothing tool. Make sure to wet your tool with soapy water before use, to stop any sealant from sticking. This will typically produce a smoother finish than using your finger.

Tips for an even smoother finish

Before laying down the sealant, apply masking tape on each side of the area you want to seal. Once applied, with the tape still in place, smooth the silicone using either your finger or the smoothing tool. Then, carefully remove the masking tape once you’re done.

Drying Time

Once a silicone sealant has been applied, you have around 10-20 minutes until it becomes unworkable and can no longer be manipulated. Although the sealant will be touch dry within an hour, it needs to be left much longer before it can be exposed to water.

It is recommended to wait at least six hours but it would be advisable to allow 24 hours for the sealant to fully dry and cure.

  • Curing time is approximately 24 hours per 4mm thickness.

Test for Waterproofing

Simply splash the sealant with some water. If the water drips and rolls down, this means the seal is still sound, and watertight. If the water looks to be penetrating the seam, try blotting the area with a paper towel. If the paper towel becomes damp, this may mean the seal is not doing its job and so it would be time to repair and reapply a fresh layer of sealant.

How to Clean Up After Using Silicone Sealant

How to Remove Excess Dried Silicone Sealant

You can choose to use a chemical silicone remover however this is not the only available option.

  • Firstly, using your hands, you can try and peel the silicone from the surface. If you aren’t able to get any traction, you can use a Stanley knife to try and carefully cut the sealant away, making sure to not scratch or damage the surface underneath.
  • If any residue is left behind, use some white spirit on a cloth to wipe away any remains. If this is not proving successful, you may need to use an abrasive scouring pad, to remove the stubborn sealant.

How to Remove Silicone Sealant From Clothes

For small amount of silicone

  • Try spot cleaning the affected areas with white spirit. Make sure to do a patch test first to ensure the white spirit won’t discolour or damage the fabric. It would be advisable to wear gloves when applying the white spirit.

For larger / thicker amounts of silicone

  • Try putting the affected item in the freezer for a couple of hours. This will speed up the hardening process, which should enable you to scrape the sealant off the clothes using a sealant remover tool.
  • After this, you should be able to get rid of any silicone residue using warm soapy water.

Maintaining Your Silicone Sealant

In order to ensure the longevity and durability of the sealant it is important to regularly maintain the condition of the seals.

Inspect the Seals Regularly:

Inspecting the seals and joins regularly for signs of deterioration and damage, enables you to identify any issues quickly so that they can be treated effectively.

Avoid Using Harsh Chemicals:

Some chemicals and cleaning agents can react with and deteriorate the sealant. It is important to opt for mild, non-abrasive chemicals where possible.

Maintain Adequate Ventilation

Ensuring there is proper ventilation helps to prevent moisture build-up, which can not only degrade the sealant but lead to the growth of black mould. Use extractor fans and dehumidifiers in areas such as bathrooms and kitchens, where there is a lot of moisture in the air. Keeping windows open can also help to promote airflow.

Clean the Surrounding Areas

Make sure to regularly clean the area surrounding the sealant to remove grease, debris, and any other contaminants that may damage the silicone sealant.

Choose a High-Quality Sealant

Before purchasing your sealant, ensure to research which product would be best for your project. Investing in a higher quality sealant from a respected, reputable brand such as Sika will not only increase the sealant longevity and resistance to environmental factors. This will, in time, be more financially beneficial as the frequency to repair and replace your seals will be reduced.

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