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.
Christina says
When preparing the Carmeuse high calcium hydrated lime for interior Limewash painting, how much lime and how much water do you recommend using? Do you let that sit with water on top for a specific amount of time before mixing with pigment and alum salt to make the actual paint to apply to the walls? Any tips or recipes are greatly appreciated!
Genevieve says
You do not need Alum to white wash. Only lime, water, and time.
I usually fill a 5 gallon bucket 3/4 full with lime powder then slowly add the cold water. This is the most dangerous part as it will create a cloud of lime dust. I make sure to be wearing all my safety gear and have a fan blowing away from me to keep the dust out of my face. I mix the water in and add more if there are dry bits of lime still. I let it settle for half an hour and if there’s lots of water on top, I add more lime. I make sure to have at least an inch of water on top once the lime settles and keep a lid on the buckets. 24 hours is best for full hydration but lime can be stored this way indefinitely and veteran lime washers say the longer you allow the lime putty to age, the better it is to work with. I just mix up a bunch of buckets as soon as I get my hydrated lime bags so it’s ready when I need it.
Kathryn says
Can you clarify, can the Graymont high calcium hydrated lime be used for limewashing? It seems to be all calcium hydroxide so would be similar to the Carmeuse product. I live in Canada and I can’t get the Carmeuse version.
Genevieve says
I don’t have experience with it but if you use it, please come back to update us so we can all learn.
Eva says
Is this the same as Mason line? I am wanting to whitewash the inside of our chicken coop, and am going crazy looking for the right hydrated lime in our area. I live in an agricultural area but everyone just has the garden stuff. TIA
Genevieve says
Yes, mason’s lime should work. If it’s a small enough coop, Pickling Lime works as well. It comes in a smaller package so you don’t have 50 lbs hanging around.
Just a heads up, lime wash on wood is not very durable. It has to be reapplied frequently as the movement in wood pops the hardened wash off.
Eva says
Thank you so much for the quick reply. I am having a very hard time finding Masons lime locally. Will try pickling. Thanks again!
Genevieve says
That’s why I ended up buying directly from Limeworks as I was spending more time and money on gas trying to find the correct stuff. Shipping is expensive but 50 lbs lasts forever when covered in water. Literally, forever.
Andrew says
Genevieve – Thanks for sharing everything… finding this stuff is more frustrating than I thought, even after reading this post!
Can you speak anything about coverage? How much does a 50 lb bag cover? I have a hearth and surround about 8’x6′ to wash. Think one bag will do?
Thanks in advance
Genevieve says
Oh for sure! A 50 lbs bag would nearly cover a 1500 sq ft house.