Fairy liquid added to mortar? Criminal or not?

EachPenny

ruhe wrote: »

Many thanks for that thorough and detailed reply which does kind of answer the question. The builder in question only used fairy liquid when they ran out of plasticizer so it wasn't or isn't a regular type of situation I don't think

ruhe wrote: »

I don't know the exact circumstance but it was just a casual conversation about it when I mentioned that I'd seen it done when I was working for a builder and I just asked him if he'd ever used it and he told me that he had when he ran out so I'd assume he was on a job and ran out and just nipped to the shop

The question is, what would he do if he ran out of bricks?

[Deleted User]

My late FIL a builder for 45 years years always added a drop of fairy, and he built houses.

abssorb

Ever noticed how all the published advice to never use washing up liquid comes from manufacturers of additives?

"Proper" plasticisers work by deliberately introducing air bubbles into the mix, which has a number of benefits. Washing up liquid does the same thing, but comes without instructions, so the big advantage is "Proper" plasticisers are less prone to human error.

But...
Th

• ey are only available in large quantites.
• They have a short shelf life of 12 to 24 months. Most builders mechants buy stock in bulk and can waste a lot of that time in stock.
• They quote silly mix parameters like "Add 5ml per 25kg of cement" (Sika maxmix) which is almost impossible to calculate on site, and then add the biggest get-out of all "the exact dosage required should be calculated by site trial".

Really? Site trial? It makes me laugh that manufacturers decry the old-hand wisdoms using science, then offer a very unscientific solution to the problem they suggest exists. It's a bit "snake oil".
More likely these are fine-print tricks so that a builder can't prove their product as a cause of failure in the event of a claim.

How many New-wave builders who insist on using "proper" plasticisers are bothering to check if their bottle is out of date? Will walls fall down as a result? None.
How much old-hand brickwork has fallen down because they used fairy liquid? None.

For DIY a bit of FL is absolutely fine. Stuff I put up (as a DIYer) 20 years ago is still a right !!!!!! to knock down.

EachPenny

abssorb wrote: »

Ever noticed how all the published advice to never use washing up liquid comes from manufacturers of additives?

Who else would you expect to publish this advice? The same advice would be given if you consulted an Engineer, Quantity Surveyor, Materials Scientist, Building Control Officer, or indeed anyone who properly understands the chemistry of OPC, the hydration process, and the qualities sought from the mortar (or concrete) mix.

abssorb wrote: »

"Proper" plasticisers work by deliberately introducing air bubbles into the mix, which has a number of benefits. Washing up liquid does the same thing, but comes without instructions, so the big advantage is "Proper" plasticisers are less prone to human error.

That is one aspect. Another, perhaps more important one, is that "proper" plasticisers are formulated with the chemicals needed to do the job, without contamination by other miscellaneous chemicals.

Do you know as a fact what the washing up liquid you use contains? Do you know whether any of the chemicals in the washing up liquid will interfere with the hydration process causing you to have weak and poor quality mortar?

abssorb wrote: »

• They are only available in large quantites.
• They have a short shelf life of 12 to 24 months. Most builders mechants buy stock in bulk and can waste a lot of that time in stock.
• They quote silly mix parameters like "Add 5ml per 25kg of cement" (Sika maxmix) which is almost impossible to calculate on site, and then add the biggest get-out of all "the exact dosage required should be calculated by site trial".

All valid points, but none of which support the use of washing up liquid instead of plasticiser.

abssorb wrote: »

Really? Site trial? It makes me laugh that manufacturers decry the old-hand wisdoms using science, then offer a very unscientific solution to the problem they suggest exists. It's a bit "snake oil".

How many New-wave builders who insist on using "proper" plasticisers are bothering to check if their bottle is out of date? Will walls fall down as a result? None.

Not sure what you mean by "old-hand wisdoms", but advice to determine the exact use of a product by 'site trial' is perfectly valid. The manufactuer is not in control of other materials to be used in the mortar. Sand type and water content also have significant impacts on the workability of mortar. A professional would be sufficiently competent to adjust the dosage of plasticiser to suit the sand/water/cement they choose to use.

There is nothing "New-wave" about using plasticiser, and nothing "New-wave" about using the correct materials to do a professional job. Before liquid plasticisers were available builders used lime. "Proper" plasticisers replaced the use of lime, they didn't replace the use of washing up liquid.

abssorb wrote: »

How much old-hand brickwork has fallen down because they used fairy liquid? None.

How do you know this? You obviously never saw the garden shed my dad built.

abssorb wrote: »

For DIY a bit of FL is absolutely fine. Stuff I put up (as a DIYer) 20 years ago is still a right !!!!!! to knock down.

If you are talking about non-structural brickwork in a DIY project then you are probably right. But then most brickwork of this nature actually needs no plasticiser at all. All the DIYer is doing is wasting money by putting expensive FL into their mortar so they can pretend to be 'professional'.

Furts

EachPenny is spot on. It is crazy that anybody should be defending putting Fairy Liquid in mortar. However, it is a useful check mechanism in the construction industry. Any "bricklayer" turning up to start a job found to have a bottle of Fairy Liquid in their toolkit with either be reprimanded and the bottle confiscated, or more likely they will be be denied work on the site. This is easy because most are sub contractors so have no grounds to complain when they are caught out for behaving like cowboys.

As for those whinging about costs, five litres is £4.59 at Toolstation, which makes the proper product cheaper than Fairy Liquid. But since when has logic, a bit of effort, and common sense, been part of the repertoire of cowboys?

Alter_ego

I use plasticiser in a Fairy Liquid bottle!

Furts

Alter_ego wrote: »

I use plasticiser in a Fairy Liquid bottle!

Keep your bottle discrete if you are working on a construction site!

[Deleted User]

EachPenny wrote: »

In terms of function the purpose of mortar is to make the masonry units (bricks/blocks) adhere to each other, so in that sense it is a kind of glue. If walls only carried vertical loads then mortar wouldn't be essential (e.g. dry stone walls), but in most buildings the walls also carry horizontal and shear loads. For a brick wall to resist horizontal loads it must have something resisting the bricks sliding over each other. This is the purpose of mortar - it fills the microscopic pores in masonry units in the same way glue does and effectively 'locks' the bricks together.

Mortar ensures that the load is spread evenly over the surface of the brick. If you stack bricks dry, the unevenness of the surfaces means that they only make contact at a few high points. Combine that with the rigidity and brittleness, and the bricks will crack and crumble when loaded. It's the same reason you shouldn't prop a car on a stack of bricks. Mortar spreads the load evenly because it conforms to the shape of the brick whilst wet.

EachPenny

Alter_ego wrote: »

I use plasticiser in a Fairy Liquid bottle!

This is one of the things which has led to the idea that using washing up liquid in mortar is something the professionals do.

There was a time where washing up liquid bottles were highly prized containers for any liquids where a 'quick squirt' was required. For example I remember my school metalwork teacher ensuring each lathe and drill was equipped with a washing up liquid bottle full of cutting fluid.

Likewise I know of many builders who found it convenient to use a washing up liquid bottle filled with plasticiser because it was easier to dose with that than pouring from a gallon tin.

These days it is not considered good practice to store or use chemicals in containers other products are supplied in (e.g. weedkiller in lemonade bottles) and in the commercial world this would almost certainly be unlawful under H&S legislation. For that reason alone a 'professional' arriving on site with a FL bottle should be sent away, unless the bottle is for washing the tea mugs.

EachPenny

genau wrote: »

Is there any scientific evidence that using fairy liquid weakens mortar at all such as scientific studies/trials at a university or is this just scientific supposition of what might happened depending on other additives in the liquid?

I went to university and did a degree in Civil Engineering. As part of the course we were taught about plasticisers, and mixed mortars and concrete and tested the properties. The lecturer explained about the illicit use of washing up liquid, but I cannot say that we actually tested samples of mortar made using fairy liquid to see how much weaker they were. We were told something by an expert and I chose to believe them.

However, we did test the outcome of using excessive amounts of plasticiser, as well as the other 'trick' of adding a bit more water to make it easier to mix and lay. That was enough to convince me.

By the same token, the students in the next lab doing Mechanical Engineering probably didn't need to be told (or carry out scientific tests) to know that using second-hand chip fat in the sump of their engines wasn't a good idea.... even though it is still 'oil' innit.

The science behind using plasticisers in mortar is sound. Part of that is seeking to obtain the optimum workability of the mortar without having an excessive water content, the other part is developing just the right level of porosity in the set mortar without creating excessive voids. Plasticiser used correctly will deliver the optimum result. Plasticiser used incorrectly can produce very bad results.

Washing up liquid comes with no instructions on the amount to use as a mortar plasticiser, so whether or not you get a good result is entirely down to chance. Since you won't know if you got it wrong until months or perhaps years later, then why take the chance when the correct product is cheap and easy to obtain?