Why Glass Ends Up Streaky in the First Place

Most streaks have far less to do with elbow grease than with what gets left behind. Tap water carries dissolved minerals, and as the water evaporates those minerals stay on the glass as a fine, cloudy film. Add too much detergent, or clean in bright sunlight so the liquid dries before you can buff it, and you get the familiar smears that seem to reappear the moment the sun comes round. The answer is not a stronger cleaner. It is a cleaner that dries away completely, paired with a cloth that lifts dirt rather than spreading it about.

The Small Kit That Does the Job

You almost certainly already own most of what you need:

• White vinegar — the clear distilled sort sold for cooking and household cleaning, not malt vinegar.
• Microfibre cloths — two or three, with one kept dry purely for buffing.
• A squeegee with a sharp, clean rubber blade, around 25–30cm wide for large panes and a smaller one for windows divided by glazing bars.
• A spray bottle, plus a bucket of warm water for outdoor glass.
• A drop of washing-up liquid for genuinely grimy outside panes or conservatory roofs.

Replace the rubber blade as soon as it nicks or hardens. A tired blade leaves a thin line across the glass that no amount of buffing will shift, and you will spend an afternoon chasing a problem that costs a couple of pounds to solve.

Mixing a Vinegar Solution That Actually Works

For everyday interior glass, dilute roughly one part white vinegar to four parts water. That is mild enough not to trouble seals or painted frames, and strong enough to cut through fingerprints, kitchen grease and the film left by candles. For kitchen windows and conservatory glass that collect cooking oils, go closer to equal parts vinegar and water.

If you live in a hard water area, use filtered or distilled water for the final rinse. It sounds fussy, but it removes the minerals that cause spotting in the first place, and it is the single change that makes the biggest difference to how long your windows stay clear.

Two warnings worth remembering. Never mix vinegar with bleach-based products, and keep it away from natural stone sills, limestone, marble and any aftermarket window film, all of which can be marked by acid. Test an inconspicuous corner first if you are unsure.

Step by Step: Interior Windows

Work on an overcast day or in the shade. Direct sun is the most common single cause of streaky results, because the solution dries before you can work it.

• Dust the glass and frame first with a dry microfibre cloth. Skipping this simply turns dust into mud.
• Spray the solution generously and leave it for ten to twenty seconds so it can soften the grime.
• Wipe in an S-pattern from the top down, turning the cloth as you go.
• Pull the squeegee down in overlapping horizontal strokes, wiping the blade on a cloth after every pass.
• Buff the edges and corners with a dry microfibre cloth, where the squeegee cannot reach.

Here is a tip worth keeping: clean the inside of a window in horizontal strokes and the outside in vertical ones. If a streak appears later, you will know instantly which side it is on without going back round the house to check.

Outdoor Glass, Frames and Sills

Outside panes collect pollen, traffic film, algae and the leftovers of every spider in the garden, so start with a bucket of warm water and a couple of drops of washing-up liquid, applied with a cloth or a soft brush on a pole. Work from the top of the frame downwards and rinse before the suds have a chance to dry. Follow with the vinegar solution and a squeegee, rinsing the blade frequently.

Wipe sills and frames as you go rather than afterwards, otherwise you simply wash dirt back onto glass you have just cleaned. On uPVC frames, a microfibre cloth and the diluted vinegar are usually plenty; avoid abrasive pads, which dull the surface and give dirt somewhere to settle. On very mucky glass, do the outside first and the inside second, so any drips land on panes still waiting to be done.

Habits That Keep Glass Clearer for Longer

A quick dry-dust of interior glass once a week with a microfibre cloth stops the film from building up, which means a full wash is needed far less often. Ventilate the kitchen while you cook, or run an extractor hood if you have one, to cut down on the grease that settles on nearby windows. Keep a cloth and a small spray bottle of diluted solution under the sink for mirrors, glass doors and cupboard fronts — a thirty-second job that saves a much longer one later.

Outdoors, clean after rain rather than before it, and tackle north-facing glass and shaded sills more often, since algae and mould prefer the damp side of the house.

Vinegar, water and a decent cloth will handle the overwhelming majority of household glass without the fumes, the plastic bottles or the expense. The method is unglamorous, but it is the one that leaves glass genuinely clear, with nothing left behind but a clean window and a little more time in your day.