Elastic silicone sealing materials have a large range of applications in and on buildings, also for the construction of wood windows: e.g. as a sealing material between glazing and casement, for the construction between the frame and the building, for window sills or for sealing coupling joints between posts and rails. Elastic silicone sealing compounds are especially suitable for these applications since they not only have many advantages when it comes to the mechanics of joints but also meet many requirements that are relevant for wood windows: high UV resistance, resistance to weather, a wide variety of colours and their ease of use....
Silicone compounds are chemically reacting products and cross-link ("vulcanise") into a soft-elastic rubber. The information on these products provided by the manufacturer will always state whether the system is acetic acid cross-linking or neutral; other special reactions no longer play a role today. Because is it acid, acetic acid attacks sensitive and alkaline substrates which leads to a loss of adhesion or discoloration.
Neutral cross-linking systems such as the product MultiSil made by Remmers Baustofftechnik are considerably more reliable when it comes to application and adhesion. They also have a mild odour so are much more pleasant to work with and also environment-friendly. Because of its elastic formulation, MultiSil is also suitable for the type of glazing normally used today without a gasket but have increased requirements on loading capacity. For the best possible results, not just a high quality product is needed; proper pre-treatment of the substrate is also a decisive criterion. Metal substrates should always be cleaned to remove grease and oil, the rebates for glazing must be dry and free of dust. When certain oily wood preservative stains have been used or the substrate is absorbent, it may be necessary to use a primer.
The edges of the glazing units should be washed off just before they are mounted in the casements with a highly volatile solvent (spirit). When the windows are installed later, loose mortar or render, chalking paint and gypsum plasterboard are not load-bearing substrates and must be removed or properly pre-treated. The "two-third rule" is the guideline for correct connection and expansion joints: the depth of the joint should be approximately 2/3 of the joint width. Example: joint width 15 mm, max. joint depth 10 mm (15 x 2/3 = 10): a joint should never be deeper than it is wide. And you should always visually check whether the freshly applied sealing material is free of air bubbles and adheres well to the sides of the joint. The surface of the sealing material can then be properly smoothed with the right tool and a smoothing agent within the skin formation time (approx. 8-12 minutes). To prevent premature damage, fresh joints should not be subjected to loads until they have thoroughly cured which generally takes about 3 days. After this time, the material is also resistant to the strong cleaners used for final cleaning.
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