Threadlocker buying guide
Updated: October 2026
You have a bolt that has worked loose, and the amazon.co.uk aisle is offering blue, green, purple, red, and a clear tube that only says Normal. This threadlocker buying guide decides the strength you can undo, what a colour is allowed to mean, and which fill you can trust, before you compare bottles. Peter F. lined up the twelve listings in our [threadlocker comparison](/hub/diy-supplies/threadlocker), from £3.99 to £12.99. He did not run a lab test. Several pages disagree with their own titles. A qualifying purchase can earn us a commission at no extra cost to you.
You have a bolt that has worked loose, and the amazon.co.uk aisle is offering blue, green, purple, red, and a clear tube that only says Normal.
You have a bolt that has worked loose, and the amazon.co.uk aisle is offering blue, green, purple, red, and a clear tube that only says Normal. This threadlocker buying guide decides the strength you can undo, what a colour is allowed to mean, and which fill you can trust, before you compare bottles. Peter F. lined up the twelve listings in our threadlocker comparison, from £3.99 to £12.99. He did not run a lab test. Several pages disagree with their own titles. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Strength | Colour | Stated fill | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Bäder Bäder B270Eco high green, 10 ml | High | Green | 10 ml | 7.6 | about £5.45 | View offer |
 Bäder Bäder B243Eco medium blue, 10 ml | Medium | Blue | 10 ml | 8.4 | about £5.39 | View offer | |
| Preis-Tipp |  kintsukuroi kintsukuroi medium blue, 50 ml | Medium | Blue | 50 ml | 6.9 | about £8.88 | View offer |
On this page
Strength before brand
If you will undo the fastener with a spanner later, start with medium strength. Low strength is the small screw and the softer metal. High strength is the fastener you intend to leave, if you can heat it later. Henkel's UK colour article treats blue as the medium grade you remove with hand tools, purple as the low grade, and green as the high grade. RS Components adds that a red liquid is often the high-strength product on other brands.
Loctite's choosing article sizes only its own grades: 222 up to M12, 243 up to M18, and 270 up to M20. Do not copy those limits onto a Bäder or Nanoxa bottle.
What the colour is allowed to mean
Read the strength word, then check that the colour cell describes the same thing. On Henkel's UK page, blue, green, and purple are the liquids, and a red bottle can be the brand's trademark rather than the dye. Bäder's high-strength 10 ml bottle is green.
The clashes are why you read the bullet. Bäder's purple 50 ml title says low, and the same bullet also says medium. The green 50 ml title says high, and the first bullet says medium. Flintronic's pair is titled blue and red, while the colour cell says blue mid-strength only. Loctite's 5 ml tube is transparent and says Normal, so it is not on a colour chart. The dye argument is on blue vs red threadlocker.
Fill, cure, and shelf life
A stated 5 ml or 10 ml bottle is a few jobs. A stated 50 ml bottle is for repeated use, if the millilitre figure is real. Loctite's tube is a 5 ml cell with 5 g in the title. Bäder's medium blue is 10 ml at £5.39 or 50 ml at £10.95. kintsukuroi is 50 ml at £8.88. The £3.99 Flintronic pages print no millilitre cell.
A half-empty bottle can be intentional air so the liquid stays liquid. Cure bullets in this set say about 10 to 20 minutes, then about 24 hours. Fixture time is not when you load the joint. How the drops go on is on how to apply threadlocker.
Metal, oil, and temperature
Threadlocker in this set is for metal threads, which is also what Henkel's UK article says. A review of the purple Bäder bottle says it is useless on plastic fittings. Do not buy these twelve for a plastic fitting, a watch link, or a food container.
Oil is a brand line. Several Bäder bullets say the liquid secures slightly oily screws. Vigorder says clean and dry. Flintronic claims oil resistance and also says clean and dry, so trust only the bottle that prints one instruction. Bäder lines here use up to 180 °C. sitarcmin prints -54 °C to 150 °C. Do not average those bands. Brakes, steering, suspension, and fuel fasteners are a mechanic's job.
What this guide will not pick
This page does not crown a bottle. Choose the strength you can undo, reject a listing whose colour cell names a different strength, and check that the temperature line belongs to that bottle. A 10 ml bottle is enough for occasional bike bolts, and a stated 50 ml bottle is for repeated use. The £3.99 pages never state a millilitre figure. Check the date before you store a large bottle.
A 243-style name is not Loctite 243. Bäder's B243Eco and B270Eco are seller names. sitarcmin's model cell prints 242/262, and the manufacturer cell is WEIKESITA. A fastener that will not move is covered on how to remove threadlocker.
Common questions
What strength should you buy if you will undo the bolt?
Buy a medium grade, or a low grade on a small screw, and check that the listing uses that word only once. Henkel and RS describe medium blue as the grade hand tools can undo. High strength, whether the dye is green or red, is the grade those sources undo with heat. If the title says low and the bullet also says medium, you do not have an answer yet.
Why do some charts say green is high and others say red is high?
Henkel's UK colour article treats green as the high-strength liquid and can use a red bottle as a trademark. RS, and the Nanoxa and sitarcmin bullets in this set, use red as a high-strength liquid. Bäder's high-strength 10 ml bottle is green. Colour is a clue. The strength word on that listing is the decision.
Does threadlocker work on plastic?
Not on the evidence in this set. Compatible-material cells say metal. Henkel's UK article is for metal. A review of the purple Bäder bottle says it will not lock plastic fittings, and watch-link reviews of the clear Loctite tube say it did not hold. A question line on a product page is not a yes.
Is a half-empty bottle underfilled?
It can be the design. kintsukuroi, Vigorder, and Nanoxa say air is left in the bottle so the anaerobic liquid stays liquid, and Nanoxa states 50 ml in a 100 ml bottle. Compare that sentence with the bottle you received. A cap that has already leaked in the bag, which UK reviews report on the £3.99 Flintronic pair, is a different fault.
Does a 243-style name mean the bottle is Loctite 243?
No. Bäder B243Eco is the seller's name on the blue bottles. The file does not say those bottles are Loctite 243. sitarcmin's 242/262 cell is the same kind of label, with WEIKESITA as the manufacturer. Loctite's M12, M18, and M20 bands stay on Loctite's grades.
Related pages
Sources
Public UK sources on colour codes, cure, removal temperatures, COSHH and GB CLP. Listing prices, stars and review themes are from the amazon.co.uk extracts dated 15 October 2026. Prices move.
- Henkel UK, blue, green and purple threadlockers (retrieved 15 October 2026)
- Loctite consumer UK, how threadlocker works (retrieved 15 October 2026)
- Henkel, how to remove high-strength threadlocker (retrieved 15 October 2026)
- LOCTITE 243 technical data sheet (retrieved 15 October 2026)
- LOCTITE 270 technical data sheet (retrieved 15 October 2026)
- ISO 10964:1993, torque method (retrieved 15 October 2026)
- HSE, COSHH assessment (retrieved 15 October 2026)
- Control of Substances Hazardous to Health Regulations 2002 (retrieved 15 October 2026)
- HSE, GB CLP (retrieved 15 October 2026)