TOSTEM

• ▸Country: Japan
• ▸Founded: 1967
• ▸Parent company: LIXIL Corporation (since 2011)
• ▸Primary material: Powder-coated aluminium sash
• ▸Market position: Japan's dominant residential window brand
• ▸Product types: Sliding sash, casement, fixed, and tilt windows
• ▸Climate context: Japan - humid summers with mould risk in tracks, cold winters, UV chalking on south/west elevations

• ▸Sliding aluminium sash (引き違い窓)
• ▸Casement sash (縦すべり出し窓)
• ▸Fixed windows (FIX窓)
• ▸TOSTEM composite windows

TOSTEM sliding sash tracks are the primary maintenance point on every Japanese residential job. The two-track aluminium channel collects a specific combination of dust, insect matter, and organic debris at the inner corners. Japan's humid summers cause this accumulation to set hard if not cleared regularly. Hard corner grime requires a brush, not just a wipe. TOSTEM powder coat is durable but not immune to Japan's UV loading. South and west-facing elevations on older TOSTEM sash show chalking - the white residue that indicates UV degradation of the coating's outer layer. This is a cosmetic and protective issue, not a cleaning one. Document it, do not attempt to scrub it off. TOSTEM windows are found across every age of Japanese residential building. Older stock from the 1970s and 1980s uses thinner, simpler powder coat. Post-2000 TOSTEM uses improved coatings. Treat older windows with more caution on abrasion.

This is how I clean TOSTEM windows. The tools and technique below come from 25 years of daily professional work on the glass. Every step has been tested on real installations and adapted specifically for TOSTEM systems.

• ✕Do not wet TOSTEM sliding tracks before brushing - wet grime becomes abrasive paste in the track channels
• ✕Do not use metal implements to clear weep holes in powder-coated track channels
• ✕Do not use abrasive pads on powder-coated sash frames
• ✕Do not attempt to scrub powder coat chalking off older TOSTEM sash - this removes the remaining UV protection
• ✕Do not pressure wash directly into sash track channels or weep holes
• ✕Do not use solvent-based products on composite TOSTEM resin profiles

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