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Blue vs red threadlocker

Updated: October 2026

You have a two-colour pack on the bench, and the bolt still has to come off next winter. Blue vs red threadlocker is a strength choice, not a price table. Choose the medium bottle when you will undo the fastener with hand tools. Treat a red bottle in this set as high strength only when that listing says so, and do not assume it is Loctite 270. The rows are on the [threadlocker medium strength comparison](/hub/diy-supplies/threadlocker-medium-strength). Peter F. compared Henkel’s UK grade guide with these listings on 15 October 2026. No bottle was torque-tested. A qualifying purchase through our links can earn us a commission at no extra cost to you.

You have a two-colour pack on the bench, and the bolt still has to come off next winter. Blue vs red threadlocker is a strength choice, not a price table.

Our top picks

Vigorder Vigorder blue 50 ml

Best overall

Vigorder Vigorder blue 50 ml
9.6/10about £7.99
View offer
Nanoxa Nanoxa blue and red 50 ml x 2

Alternative

Nanoxa Nanoxa blue and red 50 ml x 2
9.4/10about £12.99
View offer
Bäder Bäder B243Eco blue 10 ml

Preis-Tipp

Bäder Bäder B243Eco blue 10 ml
9.4/10about £5.39
View offer
On this page
  1. 1.Blue when you will service it
  2. 2.Red when you do not plan to undo it
  3. 3.Amazon red is not Loctite 270
  4. 4.If it will not move

Blue when you will service it

Blue, in Henkel’s UK choosing guide, is the colour of Loctite 243, the medium-strength grade you remove with hand tools. Low strength is Loctite 222, often purple. In this set that is true only when the bullet says so. sitarcmin says the blue liquid can be disassembled with tools. Nanoxa calls the blue locker removable. Flintronic’s shared bullet says medium strength comes off with standard tools. Bäder’s UK reviews say screws could still be undone, and the bullets do not print hand tools. Checks that are not about colour sit on the medium strength threadlocker buying guide. The dosing order is on how to apply threadlocker.

Red when you do not plan to undo it

Red, on the listings in this set, is the high-strength or permanent bottle. Nanoxa calls the red locker permanent. sitarcmin says the red liquid is for permanent fixing. Flintronic’s bullet says high strength needs heat, then standard tools. One UK review on the row whose colour cell says Red (HI-Strength) calls it a permanent lock. Stronger is not safer. Henkel’s high-strength grade is Loctite 270, and that bottle is green, not red. It may need heat. If the bolt is one you will see again, red is the wrong bottle. Realth’s three-pack calls purple a temporary fix and high a permanent project, and its compatible-material cell says Plastic.
Vigorder Vigorder blue 50 ml

Testsieger

Vigorder Vigorder blue 50 ml
9.6/10about £7.99
View offer

Amazon red is not Loctite 270

Henkel’s UK article prints 270 as green. ConRo’s note calls 270 red in one place, which fights Henkel’s green. Amazon red in this set is a listing colour. It is not Loctite 270 or a US 271. The Flintronic red title says medium and high, while the colour cell says Red (HI-Strength). The 4.3 from 24 reviews on that row is its own star line. The 4.6 from 381 on the other Flintronic ASINs is one shared file. Bike jobs that still come apart are on the threadlocker for bike bolts page.

If it will not move

Start with hand tools if you used a medium-strength bottle. ConRo’s note gives about 250°C for a high-strength 270-class lock, and the same article calls 270 red. Henkel’s US page talks about localised heat above about 250°C for US red grades. Neither page is a blowtorch guide for a UK brake or a fuel fitting. Do not heat a bolt near fuel, a sensor, plastic or fresh paint yourself. That is where a professional should take over. If you already used the red bottle on a bolt you must service, say which bottle. On an ordinary cover, hand tools come first.

Common questions

Is blue always medium and red always permanent?
No. Henkel’s UK guide uses blue for medium-strength 243 and green for high-strength 270. In this amazon.co.uk set, several red bottles are sold as high strength or permanent, and that is a listing colour, not a proof of grade 270. A blue bottle still has to say medium strength, or show UK reviews of later removal, before you trust the cap. Loctite Normal’s colour cell says Transparent and does not print 243.
Can you undo blue with a spanner?
When the listing says so. sitarcmin says tools. Flintronic’s medium line says standard tools. Henkel says hand tools for 243. Bäder’s bullets do not print that sentence, though UK reviews say the screws could still be undone. If neither the bullet nor a review on that ASIN says it comes apart, you do not have the promise. A spanner on a high-strength red lock is how people round a head.
Does red need heat?
The high-strength bullets in this set say heat, then tools. Flintronic prints that. Nanoxa and sitarcmin call red permanent and do not give you a home heat procedure. ConRo and a Henkel US page cite about 250°C for high-strength or US red grades. That is their figure, not a licence to heat a bolt near fuel, paint or a sensor. Hand tools come first on a medium lock. Heat on a permanent lock is a professional job in those places.
Is Loctite 270 red or green?
Green, in Henkel’s UK choosing guide. Silmid’s brochure shows 270 green and 277 red. A US article about red threadlocker is about other grades, such as 271. Some distributors have called 270 red, and that slip is why a red Amazon bottle gets mistaken for 270. Buy 270 by the grade number and Henkel’s colour, not by a red cap in a two-bottle set.
Is stronger always safer?
No. A high-strength lock on a bolt you must service is harder to remove and can need heat beside parts that hate heat. Medium strength is the safer choice when the fastener has to come apart with hand tools and the manual does not demand a permanent grade. Stronger only matches a joint that is meant to stay. The manual, not the word heavy-duty on a bullet, decides that.
What if you already used the red bottle on a bolt you must service?
Stop if it is near fuel, paint, a sensor or a brake, and tell a professional which bottle you used. Do not add a torch because a US page mentioned 250°C. On an ordinary cover, hand tools come first if you might have used the medium bottle. If it was the permanent red, heat is the route those sources describe, and it is not a job to improvise next to a fuel line.

Related pages

Threadlocker comparison

Threadlocker medium strength

Best medium strength threadlocker for a bolt you undo

Threadlocker for bike bolts you still need to service

Medium strength threadlocker buying guide for a bolt

How to apply threadlocker so the bolt still comes apart

Sources

Henkel, the Health and Safety Executive, ISO 10964 and the Consumer Rights Act 2015, plus the amazon.co.uk listings read on 15 October 2026. Prices move. Nothing was torque-tested in a lab.

  1. Henkel UK, LOCTITE 243 (retrieved 15 October 2026)
  2. Henkel UK, choosing a threadlocker (retrieved 15 October 2026)
  3. Henkel GB SDS 817149, 11 June 2026 (retrieved 15 October 2026)
  4. HSE, GB CLP (retrieved 15 October 2026)
  5. HSE, COSHH (retrieved 15 October 2026)
  6. ISO 10964:1993 (retrieved 15 October 2026)
  7. Consumer Rights Act 2015 (retrieved 15 October 2026)
  8. Permatex medium strength threadlocker blue (retrieved 15 October 2026)
  9. amazon.co.uk listings, example Bäder B0CFR456YL (retrieved 15 October 2026)