Silicone sealant questions
Answers to what fabricators, contractors and consultants ask us most. Can't find yours? WhatsApp us.
What is the difference between neutral cure and acid cure silicone?
Acid cure (acetoxy) silicone releases acetic acid as it cures, which is the vinegar smell. It can corrode metals and react with alkaline surfaces such as concrete and mortar. Neutral cure silicone does not release acid, so it is the safer choice for aluminium window frames, metal, concrete and most building work. LC909N, TOPP and KCC SL907 are all neutral cure.
Should I use LC909N or TOPP?
WACKER LC909N is a general-purpose glazing sealant for setting glass and sealing aluminium, UPVC and wooden windows (movement capability 20%, KS F 4910 G-30SHM). TOPP is a weatherproofing sealant for joints that move more and face the weather: window perimeters, aluminium panels and curtain wall joints (movement capability ±30%, KS F 4910 F-25HM, tested to BS 5889 and BS 3712). If you are not sure, WhatsApp us a photo of the joint.
How long does the silicone take to dry?
For LC909N and TOPP, a skin forms in about 10 minutes and the sealant cures inwards at about 2 mm a day, measured at 23 °C and 50% relative humidity. A deeper joint takes longer to cure all the way through, and cold or dry weather slows it down. Avoid moving or loading the joint until it has fully cured.
What is BS 5889 and which product meets it?
BS 5889 is the British Standard specification for one-part, gun-grade silicone building sealants, and Hong Kong specifications often refer to it. In 2025, Fugro's Hong Kong laboratory tested TOPP to BS 5889:1989 and BS 3712:1985, and it passed every test. You can download the report from the technical data page.
What colours are available?
LC909N: white, grey, black and dark bronze, plus unfilled transparent and translucent. TOPP: champagne, white, grey, black and bronze. KCC SL907 Premium: white and clear. Ask us about other colours.
Can I use LC909N on mirrors, natural stone or aquariums?
No. WACKER advises against using LC909N for mirror bonding, insulating glass units, structural glazing, natural stone such as marble or granite (it can stain), aquariums or long-term underwater use, and food-contact joints. Tell us the job and we will suggest a suitable product.
Are you an authorised distributor?
Yes. LH-HY is the sole authorised distributor of WACKER silicone sealants in Hong Kong, certified by Wacker Chemicals Korea, and an authorised distributor of KCC. TOPP is our own brand, made for us by WACKER in Korea. We can send a copy of the distributor certificate on request.
Do you have documents for project approval?
Yes. The technical data page has the TOPP BS 5889 / BS 3712 test report, the LC909N KS F 4910 test report, the product leaflet and safety data sheets. If your consultant needs anything else, ask us.
How should the sealant be stored?
Keep cartridges in a dry, cool place away from direct sunlight, ideally between 5 °C and 30 °C, and use them before the date on the label. LC909N cartridges keep for 12 months from production.
How do I get a price?
WhatsApp us on +852 5525 5140, call +852 3620 2080 or use the enquiry form. Tell us the product, colour and quantity. Our office on Nathan Road, Mong Kok is open Monday to Friday, 9:00 am to 5:00 pm.