We"ve all heard about uthe "vinegar test" for determining lime or cement, but it's really not just as simple as opening you kitchen cupboards and

taking a small piece of the plaster, render, Mortar or whatever else you are unsure of, putting it in a bowl or on a plate and simply adding vinegar to it. The simple thinking behind this is  that lime is an Alkaline and Vinegar is an Acid so the two will react with one another, and this is seen by 'fizzing' of the Vinegar (the acid) but there's a big, but little mentioned thing that simply does  not make this as simple as the  arnchair experts like to make out: it may be a thinking, but it's certainly not science.

First we need to understand what OPC means and what cement is made of

OPC is the common abbreviation used in the construction industry for Ordinary Portland Cement - Approximately 40% to 60% of 'cement' is actually limestone which has been heated in a kiln to drive out moisture and CO², and then crushed to a powder, and this  is what gives cement the bulk of it's  calcium content.

•  About 20-25% of cement includes clay, silicates, aluminates, and/or iron oxides.
• Some manufacturing plants will also mix in  ground shells, to further increse the calcium content.
• Silicates account for around 5-10% of the overall cement mix, increasing both  it's  strength and durability.

(Hopefully you will have noticed that there's quite a large Elephant already in in the room!) 

Limestone is, as the name says, Lime, so how do you know that the vinegar

'fizz' is really because it's pure lime or an older, deteriorated cement?

Another issue to be aware of is that cement and lime have been a regular mix since the late 1800's, frequently used in early cavity walls (sorry, but the pre 1900 soildcwalls / post 1900 cavity wall nonsense is also just not true) to create a pH neutral mix (calcium carbonate,  7 on the pH scale) which wouldn't corrode the early steel cavity wall ties, (there is of course acid erosion, but Alkaline erosion is also very real, so in these instances which one is your 'magic' kitchen test going to choose?

Vinegar contains natural Axetic Acid, in fact it comprises of around 8% Acetic acid. Hydrochloric acid will dissolve lime,  but Hydrochloric acid ostensibly hits  around 40% Acid content  -  vinegar doesn't come anywhere near!

But at least today's arnchair experts are entertaining in their ignorance, if nothing else 🤣🤣