Identify mortar - lime or not

[mri_ice]

Hi all,

I need to do some pointing patch repair to a few places, and trying to identify what might have been used originally.

House is ca 1950s ex-council house.

The weather-facing front (front.jpeg) has a distinctly different look-and-feel to the back of the house (back.jpeg), which is much more yellow and crumbly.
Might this just be different sand that was used?

I'm mostly trying to identify whether it looks like lime might have been involved. I don't really think so, and was therefore intending to patch with a 4:1 sand/mortar mix. Does that sound about right?

Many thanks

Martin

 

[Roy Bloom]

Lime is an alkaline material, and will fizz violently in acid. Chip off a small section of mortar, and drop it in a dish of white vinegar. If it fizzes violently, it’s most likely lime!

Lime Pointing — Rosie and the Farm

Repointing is a technique used to ‘finish’ the gaps between stone or brick in construction. It uses mortar, which is a workable paste made by combining a binding material such as lime, cement, or earth, with an aggregate, most commonly sand, and water. Mortars are used in the construction of walls,

www.rosieandthefarm.co.uk

 

[opps]

I am not a pointer, I am a decorator, but I spend a lot of time on site with a very, very good pointer.

Image number 1, you need white cement. I think on the current job they are using 3 to 1. The colour of the sand has a bearing though.

They then plan to use brick acid to remove the smudges, it will make the mortar slightly lighter.

 

[^woody^]

They would not have used white cement when built. The sand would determine the colour - buff sand, and it would be sharper than we use nowadays so lighter.

Acid won't make mortar lighter, but will clean it - while eating away the cement and weakening the weather resistance - and opening pores to collect dirt to then darken it!

And 3:1 is way too strong for face work - that will erode the brick arrises in short time.

Back to the OP, 1950 is a bit late for lime mortar, but not impossible. However, lime may well be stronger due to exposure than it would be when sheltered. You'll need to test it.

 

[noseall]

Looks like standard 4 or 5:1 yellow sand muck to me.

 

[opps]

And 3:1 is way too strong for face work - that will erode the brick arrises in short time.

They are using 3:1 for the white cement and 4:1 for the grey pointing (with grey sand).

They are using the same sand for both mixes. The house was repointed about 20 years ago. The neighbours told me that the previous owners were unhappy with the fact that it was so yellow.

Colin the pointer is patch pointing the yellow. The colour match is impressive but he says that a dilute coat of patio acid will lighten it and remove any smudges.

I have no reason to doubt him, I have seen dozens of houses in Ealing that he has pointed, some 30 years ago. Both the red rubber bricks and pointing are in good condition.

His work is stunning, I can walk around ealing and spot his weather struck pointing with a 90% likelihood of being correct.