Lime mortar colour

[overlander matt]

We started repointing our Georgian house 5 years ago and selected a pre-mixed lime from Anglian Lime Company that was a reasonably good match to some existing areas of the house. The aggregate content was fairly fine and suited to the smaller joints in the brickwork. The colour match was reasonable - it's still white but gradually losing its brightness. My current focus is on rebuilding and repairing garden walls but the expense of buying premixed lime from Suffolk is not really an option so I'm looking at using local shard sands and mixing my own. The 3:1 sand to lime mixes are all a bit grey and wonder what I can do to get a whiter finish. I've used various different sharp sands - some grey, some yellow and another red but the end result is greyer than I would ideally want. How do others get on with mixing their own mortars to get the right colour?

Thank you in advance.

Matt

 

[stuart45]

Which lime are you using?

 

[aockenden]

If you want a whiter dry mortar colour, go from a 3:1 ratio of sand to lime to a 2:1 ratio of sand to lime. More lime = more white. I don't use 3:1 for anything anymore personally.

Also switch to a lime with a higher free-lime content. So if you're using an NHL then I'd recommend Saint Astier NHL 2 which is VERY white relative to the trashier low-quality NHLs on the market. Or alternatively, switch from an NHL to a non-Hydraulic lime putty.

 

[aockenden]

Here’s a side-by-side of two NHL’s. One is Saint Astier, the other is a trashy builders-merchant NHL which shall remain nameless.

Any guesses which one is Saint Astier?

 

[stuart45]

The colour of mortar also changes with the way the joints are finished.
Using a churn brush exposes the aggregate, so is slightly different to when a metal tool is used to finish, as this brings a lime laitance to the surface which is usually whiter.

 

[a twig]

Here’s a side-by-side of two NHL’s. One is Saint Astier, the other is a trashy builders-merchant NHL which shall remain nameless.

Any guesses which one is Saint Astier?

View attachment 13518

St “ahhh it’s blinding”stier on the left perchance?

 

[aockenden]

St “ahhh it’s blinding”stier on the left perchance?

Lol yep

 

[malcolm]

The colour normally has more to do with the local sand. Even the builders merchants still tend to supply local sand as it's heavy and expensive to move too far. We have quite a dark sand around here so the lime mortar is a light brown. Even the cement pointed building have a nice brown tinge rather than the normal grey.

I suspect if you really want white you'll need to import sand in the form of a pre-mix.

 

[Stevers]

Silver Sand, as sometimes sold for childrens sand pits would be worth a try - if you can source it.

I've used a lot of different NHLs (all 3.5), and none I haven't liked.

 

[Kearn]

Sand sand sand. That’s really the key, and once you find what you want, grab it as many merchants change with the quarries. Even their pre bagged vs loose is completely different!

 

[noj]

Don't forget that lime gets lighter over a period as it dries and carbonates (at least weeks, generally months)

 

[overlander matt]

Thanks for the answers! I have used various from different lime companies. The current batch is Saint Astier and I am on the last few bags of the pallet. I can certainly increase the lime content to 2:1 for a whiter finish but there is a cost implication to this - there are many walls that need rebuilding and others that need to be pointed so getting the right look for the right price would be ideal. I've also considered adding a hydrated lime to the mix which I believe will soften the NHL 3.5 mix but have yet to explore this option.

A lighter sand would be the ideal solution. It's just a matter of finding it. I've inserted a picture showing a mortar used for repointing on the left and a small section of the greyer lime with the locally available sharp sand. The picture isn't great in terms of the colour but gives a rough idea. From what I hear, the sharp sand is fairly consistent so should be available for some time to come - I hope! I'm not looking for a perfect match but a whiter shade would be good to settle on for all this garden wall work to come.

Thanks again for the ideas.

 

[a twig]

At the risk of being helpful, white silica sand would get you the colour you are after but obviously more costly than general builders sand.

If you are currently doing a 3 building sand :1 lime, swapping one of the 3 builders sand with the white silica would probably get you most of the way there while minimising cost.

 

[overlander matt]

Thanks for that suggestion! That is indeed helpful. My problem is that I don't seem to be able to get white silica sand in the area (near Derby) without paying for a pallet shipment. This is still likely to be more economical than increasing the lime:sand ratio.

Next step is to find a reasonably prices supplier... Hopefully will be able to lay a few bricks next week.

 

[a twig]

Good luck and keep us posted, always great to see how these things turn out

 

[overlander matt]

Thanks! I've ordered in a large bag of the white sand so will give that a try... At £200 a delivered bag it is not ideal but it's somewhere to start! I'll try out a few different blends to see what provides a good colour match at a reasonable price.

I did get to visit the original supplier yesterday in Suffolk and discovered that the original blend of premix is no longer available as the pit has now closed. I still have a few small bags left of the blend but they're a couple of years old now. Although they've been stored inside in a dry place, I really don't know how long they are likely to be usable for. Unfortunately, I never finished pointing the house with this mix so my matching skills will need to improve!

I'll keep you posted on findings. Thanks.