Application of Sealants
1. Design of joints:
In case of joints that have to accommodate movement, the dimensions must be chosen according to the maximum movement tolerance. A minimum joint cross section of 3 × 5 mm is required. Joints with little total deformation (5 %) can also be designed as triangular joints. Since there is no silicone sealant for universal application, the decision on what system to use must be made taking into account the characteristics of the respective project (adhesion tests are recommended). The adherent surfaces must have sufficient load bearing capacity, and must be dry and free from dust and grease. Prime the surfaces thoroughly if necessary. The compatibility of the sealant with the substrate must be tested. Tarry and bituminous substrates are not suitable for use as adherent surfaces.
2. Cover the joint edges
Cover the joint edges accurately on both sides by means of flat masking tape. Press the adhesive tape firmly against the surface.
3. Primer coat
If the substrate offers poor adhesion, apply a primer coat. Choose the primer according to the primer table. It is recommended to conduct a new adhesion test afterwards. Stir or shake the adhesion-enhancing primer well. Apply it to the cleaned and dry silicone surfaces in the undiluted state, using a paintbrush or cloth. Protect treated surfaces from moisture and dust. After sufficient open time (see the respective product label), apply the sealant. Adhesion-enhancing primers form a film and cannot be removed after curing.
Therefore, work with great care to avoid undesirable effects (yellow discolouration, stains). Exercise caution with substrates sensitive to solvents, e.g., powder coated surfaces, sanitary plastic materials, styrofoam, etc.
4. Profiles for deeper joints
In most cases, joints in buildings are much deeper than required, and therefore they are not suitable for efficient sealing. Expansion joints in building construction must be designed according to DIN 18540. Ramsauer closed-cell round profiles comply with this DIN standard. As a pre-filler, the product must have the required characteristics to prevent three-edge adhesion, it must not affect the sealant, and it must not absorb any water. The round cord must be selected according to the joint width and must be placed inside the joint. When introducing the profiles into the joints make sure that the sections are compressed by about 25 % (in order to secure them). Do not introduce the cord by means of sharp objects, since this will damage the surface (danger of the formation of blisters).
5. + 6. Open the cartridge
Open the cartridge (cut off the threaded stem) and trim the nozzle to an oblique angle according to the joint width.
7. Introducing the sealant
Introduce the sealant into the joint evenly and without blisters within the timeframe of its pot life.
8. Touching up
In touching up, ensure good contact with the adherent surfaces/joint edges. When using smoothing agents, remove any resulting streaks of water immediately after sealing.
If you wait too long to clean, permanent streaks may remain. Using household detergents as smoothers may cause problems since the ingredients of these products include chemicals that may cause discolouring or even the destruction of the sealant surface.
It is absolutely necessary to ensure that no smoother penetrates into the joint before it is filled with sealant. This would reduce or even prevent adhesion of the subsequently introduced sealant.
We recommend our smoothers „SANITARY 505“ and „SPECIAL 506“. Unfortunately, smoothing of sealants with one’s fingers is still a commonly employed practice. In order to prevent the related technical and hygienic disadvantages, suitable tools (glaziers spreader, special joint smoothing tools such as “Fugenprofi”, “Fugenfux”, “Glättfix”, etc.) should be used. Make sure that the adhesive tape is removed before a skin is formed.
Maintenance of elastic joints sealed with spray sealant: Check joints at regular intervals and repair or renew them as required. If no defects can be detected, no maintenance work will be necessary. Due to the build-up of an electrostatic charge in silicone sealants, dust and dirt particles are attracted to the silicone surface. It is absolutely necessary to clean the joint using a moist cloth. Dry cleaning may entail the so-called “eraser effect” (abrasion of material from the silicone surface). Commercially available cleaning agents can be used (take resistance to chemicals into account!).
Excessive mechanical stress or exposure to chemicals, incompatibility with the substrate, or inexpert application may result in defects such as detaching from the adherent surface, longitudinal and transverse cracks in the sealant, visual defects, etc. Any such defect must be remedied professionally as soon as possible.