Monsoon Damp & Mildew

Interlining is the single worst decision in a Goan monsoon. It is a thick absorbent layer sealed between two other layers, with no way to dry, and it will hold water for months. Whatever it does for the drape of a curtain in a temperate climate, it is the wrong construction here.

Foam-backed blackout lining is nearly as bad. The coating is a vapour barrier, so any moisture that reaches the face fabric cannot escape through the back. It also degrades in sustained heat and humidity, cracking and shedding after a couple of seasons.

Three-pass acrylic-coated blackout is considerably better because it breathes to a degree, but where genuine darkness is needed we would usually rather put a separate blackout roller behind a plain curtain and keep the two functions apart.

IMD's normals for the state capital record morning relative humidity of 88 percent in June and 91 percent in July, August and September, with afternoon readings only a few points lower. About 91 percent of the year's rain falls in those four months, and July alone brings roughly a third of it.

Set against that, the US EPA recommends keeping indoor humidity below 60 percent, and research on building materials treats sustained surface humidity above about 80 percent as the point where mould becomes likely. A naturally ventilated Goan house in the monsoon sits above every one of these thresholds for weeks at a time. The goal is therefore not to prevent damp air, which is impossible, but to stop fabric staying damp.

The rooms most at risk share a few features: external walls on the windward side, ground floors with a damp slab, rooms kept closed for privacy or air conditioning that is switched off for long periods, and any space where furniture is pushed against an outside wall. We walk the house in the dry season looking for old tide marks, flaking paint and dark corners, because last year's damp is the best predictor of this year's.

Touch is a useful instrument. An external wall that feels distinctly cooler than an internal one in May will be cooler still in July, and anything hung flat against it will be the first to spot. Note these walls and plan an air gap for every treatment on them. Finally, check what is already hanging. Inspect linings, the back of pleats and hem turnings closely. Faint grey freckling in these places means last season's growth is still present and will restart quickly once humidity rises.

Polyester and polyester-rich blends are the most forgiving face fabrics because the fibre absorbs very little water and dries quickly after a humid night. The trade-off is handle: some polyesters look flat or shiny, so it is worth seeing a large sample in daylight rather than choosing from a small swatch.

Cotton and linen can work in a well-ventilated, occupied room, especially unlined and hung clear of the wall, but they are the first fabrics to spot if conditions slip. They are a considered choice for rooms with good cross-draught, not a default for every window. For linings, a lightweight polyester-cotton or pure polyester lining protects the face fabric from sun without adding much absorbent mass. Leaving curtains unlined in a room that does not need darkness is also a legitimate choice here, not a shortcut.

Before the onset, usually in the first week of June near the coast, wash curtains so they go into the season clean, confirm hems clear the floor, and check that brackets hold fabric off the wall. Clear gutters and check window seals, because a leak onto a curtain is far worse than humid air.

Through June and July, draw everything fully back on any day with a break in the rain and run ceiling fans in closed rooms for a few hours. In August, which still averages around 25 rainy days, pull curtains away from external walls and inspect the wall side and the hem; this is when early spotting can still be dealt with. After withdrawal in mid-October, wash everything that hung through the season and dry it thoroughly in shade before rehanging.

Early growth on synthetic fabric often lifts with a normal wash followed by thorough drying in shade and moving air. Treat the curtain promptly, because spores spread readily to neighbouring fabric, and brush off any dry surface growth outdoors before washing rather than indoors. On cotton and linen, established spots often leave a permanent stain even when the growth is killed, and strong bleach weakens the fibre and strips colour. Test any treatment on a hem allowance first. Where a lining is badly affected but the face fabric is sound, relining is usually more sensible than replacing the whole curtain.

Whatever the treatment, the cause has to change too. Cleaning a curtain and rehanging it flat against the same cold wall simply restarts the process. Move it off the wall with deeper brackets, shorten a pooling hem, remove any interlining, and keep up the daily routine of drawing it back, so the conditions that allowed growth are gone before the curtain goes back up.