Learning how to sterilise a grow room with isopropyl alcohol is one of the simplest ways to reset a space between growing cycles. A build-up of residue, mould spores and pest eggs on hard surfaces gives problems somewhere to hide, and a proper sterilising wipe-down with GROWTH TECHNOLOGY 99.9% IPA breaks that cycle before your next crop goes in. The same bottle earns its keep on trimming scissors too, dissolving sticky resin that dulls blades and slows down harvest. This guide covers mixing the correct 7:3 sterilising dilution, wiping down walls, ceiling and floor safely, and step-by-step scissor sterilising for a sharper, more hygienic trim.
๐งด Why Dilution Ratio Matters for Sterilising with IPA
GROWTH TECHNOLOGY IPA is 99.9% pure isopropyl alcohol, designed for sanitising surfaces, cleaning tools, and oil extraction from herbs. Used neat, high-purity IPA evaporates very fast, which is useful for wiping electronics but gives the alcohol too little contact time to reliably kill mould spores and bacteria on a surface.
For sterilising, the alcohol needs to stay wet on the surface long enough to do its job. That's achieved by diluting GROWTH TECHNOLOGY 99.9% IPA down to a 7:3 ratio โ 7 parts IPA to 3 parts water โ which brings it to roughly 70% strength. The added water slows evaporation and improves contact time, making it more effective against pathogens than using the alcohol at full strength.
๐งฝ How to Sterilise an Empty Grow Room
1. Clear and pre-clean the space
Remove all plants, pots, trellising and equipment before you start. Sweep or, ideally, vacuum the floor, walls and corners first โ sterilising solutions work best on a surface that's already free of loose organic matter, dust and debris.
2. Mix your GROWTH TECHNOLOGY IPA sterilising solution
Combine 700ml of GROWTH TECHNOLOGY IPA with 300ml of water to make 1L of sterilising solution. Scale the same 7:3 ratio up or down as needed โ for example, 350ml IPA to 150ml water makes 500ml of solution. Mix only what you'll use in the session, as diluted IPA doesn't keep the same shelf life as the concentrated product.
3. Wipe down walls, ceiling and floor
Spray one wall or section at a time and leave the solution on the surface for a short contact time before wiping down with a clean cloth or sponge, working corners and seams where debris tends to collect. For the ceiling, a dampened cloth or sterilising wipe is safer than spraying upward, reducing the risk of the solution running back down onto your face or into your eyes.
Finish with the floor, including underneath any removable floor trays, and allow every surface to air dry fully before bringing plants, pots or equipment back in.
4. Follow basic safety precautions
Isopropyl alcohol is flammable, so keep the room well ventilated and away from any naked flames, hot lights or ignition sources while sterilising. Avoid spraying directly onto electrical fittings, fans or lighting โ wipe these down instead with a lightly dampened cloth.
๐ก A-Grade Tip: Work through the room in the same order every time โ walls, then ceiling, then floor โ so you don't accidentally re-contaminate a surface you've already sterilised.
โ๏ธ How to Sterilise Trimming Scissors
Sticky trimming scissors are a common source of cross-contamination between plants, and resin build-up on the blades also blunts your cutting edge over time.
1. Scrape off heavy resin first
Use a razor blade or scalpel to gently scrape off any thick resin build-up before soaking. This stops the resin from clouding your sterilising solution and makes the soak far more effective.
2. Soak the blades in your 7:3 IPA solution
Submerge just the blades โ not the handles โ in a small container of your 700ml IPA : 300ml water sterilising mix. A short soak of 30โ60 seconds is usually enough for light resin, while heavier build-up benefits from 15โ30 minutes.
3. Wipe, dry and store
Wipe the blades clean with a soft cloth or paper towel and allow them to dry fully before use or storage. Don't rinse metal blades with water afterwards โ it invites rust, whereas the IPA solution evaporates cleanly on its own.
Alcohol-based sanitising of cutting tools doesn't require a prolonged soak to be effective, which is why quick dips work well for routine, between-plant sterilising rather than only end-of-harvest deep cleans.
๐ก A-Grade Tip: Keep two or three pairs of scissors in rotation during a big harvest โ while one pair soaks in your GROWTH TECHNOLOGY IPA sterilising solution, you can keep trimming with a clean pair and swap them through.
Keeping It Up Between Cycles
A consistent sterilising routine โ a 7:3 GROWTH TECHNOLOGY IPA solution on walls, ceiling and floor, and a quick soak for tools โ is one of the easiest ways to cut down on mould, pests and cross-contamination between grows. Disease-causing pathogens can survive in leftover organic matter and on hard surfaces, so cleaning and sterilising in between grows is essential.
GROWTH TECHNOLOGY 99.9% IPA is available from A-Grade Hydroponics in 1L and 5L sizes for in-store pickup. Pop into the Cheltenham store or get in touch with the team if you have questions about sterilising ratios for your setup.
