Finding the correct Hydrated Lime for limewashing brick fireplaces and walls can be very confusing and downright frustrating with so many products sharing “Hydrated Lime” name. Hydrated Lime for Gardening/Agriculture is not the same as Hydrated Lime Type S and neither are High Calcium Hydrated Lime, used for whitewashing bricks. Yes, they are all white powders, but they are completely different substances. Knowing the difference is vital for successfully whitewashing brick fireplaces and homes.
Finding High Calcium Hydrated Lime for whitewashing brick can be a frustrating endeavor, especially when the salespeople at the hardware store are untrained. I went through this recently at my local Ace. I bought high calcium hydrated lime there last year without trouble but when I went to pick up more, they had a completely different brand with labeling “For Agricultural Use” made by OldCastle Stone Pro
I tried to explain that ag lime was not the same as hydrated lime for masonry use but they kept on. It was the beginning of the COVID-19 epidemic so instead of risking infection further, I said “Fine, load it.” As soon as I got home, I mixed a sample with water and instantly knew it was not the same. For a great explanation of the different types of hydrated limes available, this is from the International Building Lime Symposium 2005 “Limewash: Compatible Coverings for Masonry and Stucco”
In many parts of the world, hydrated lime is made from limestone with a very high calcium content (95%+) and is known as high-calcium lime.
Uniquely in the United States, hydrated lime for building construction applications is made from dolomite (magnesium-containing limestone) and is slaked in pressure hydrators or by secondary steam processing that results in a lime of the very finest particle size. This lime is ready for immediate use and is so special that it is given an ASTM designation of Type S, Special Hydrated Lime. High-calcium hydrated lime in the U.S. may be designated as Type N, for Normal Hydrated Lime, and will require a soaking period of at least 24 hours in water prior to use.
Peter Mold & Richard Godbey
Dolomite Lime is not the same as High Calcium Hydrated Lime
Click on this link to see the differences in the types of Limes.
| Brand | Type | Chemical Makeup | Info |
| Greymont (also sold under Western Miracle brand name) | High-Calcium Hydrated Lime | Calcium hydroxide | SDS |
| Dolomitic Hydrated Lime Type S | Calcium magnesium hydroxide | Technical Info | |
| Chemstar (owned by Lhoist) | Type S | Technical Info | |
| Carmeuse | High Calcium Hydrated Lime | 85% Calcium hydroxide | SDS |
Jeremy G says
I’m still a bit confused. We’re interested in limewashing our brick fireplace surround & an interior brick wall. Can we use Type S hydrated lime to make the lime wash? or will that not work correctly? Thanks!
Genevieve says
Purchasing hydrated lime is very confusing. The US does not regulate what can be called hydrated lime, unlike in the EU where there are strict standards.
The only hydrated lime I can recommend is the High Calcium Hydrated Lime by Carmeuse which can be purchased from Limeworks or if you are lucky like me, from a local hardware store.
Karen says
Genevieve, I noticed the kind you recommended above is Type N. Everything I’m reading about limewashing brick mentions type S. Since you’ve used all the above products, do you know if both type S or N work for that? I’m confused about it. We’re having a hard time getting it here. I don’t want to waste money on the wrong stuff. Thanks for the help
Genevieve says
Buy the high calcium lime from Limeworks or see if your local hardware store (not big box) has Carmeuse High Calcium lime. You’re going to pull your hair out trying to find the right stuff from a different company. The bag has to explicitly say “high calcium”.
Save your time, money, and sanity by just ordering from Limeworks. (I have zero affiliation with them and don’t earn commissions through sales. They are the only consistent source of high calcium lime online.)
Karen says
Ok and thanks for your input!! My concern is you mentioned to someone else that type S is not pure white. We watched a YouTube video of a woman who used Type S hydrated lime from Lowe’s and she added a glass of brewed coffee and some water to her mix, nothing else. Hers came out a creamy white, which is the look we’re going for. Hoping we can do the same to the Type N and it will
come out kinda creamy off white. We don’t plan on using the other powder you added either. I was initially excited thinking about doing this project but it’s been difficult finding the line and researching it that it’s all overwhelming to me now. 😕 thanks again so much!
Genevieve says
For the love of…no. Just no. Coffee is not a lime stable colorant. Coffee isn’t even UV stable. It may have been “creamy” the day it cures but in a year it will not be that color at all. This is why I never publish a blog post until I’ve thoroughly tested the process for at least a year. Too many bloggers are throwing crap like this up without testing.
This is a link to colorants you can add to limewash: Lime Stable Pigments
Carol says
What will happen if I use garden lime and salt to make limewash?
Genevieve says
It wouldn’t carbonate thus will not adhere to your surface. Salt is unneeded and can be detrimental to the base surface, exposed pipes, and surrounding soil.
High calcium hydrated lime powder or lime putty + water is literally the only thing you need to properly lime wash porous surfaces.