Homebrew set-up time??

[Bread]

Hi everyone!
I went out today to lay the second course of sailors, (I am stacking three sailors to gain some wall height before my dome starts. I surrounded my oven floor with the first course) as I buttered up my first brick with my Homebrew (3:1:1:1 mix) and put it down. I gave it a few taps with my rubber mallet I broke a few bonds on the course below. I lifted the first course off the insulation board. Some joints held and some joints broke off. The mortar would flake clean on one side of the brick and I could tap off the mortar on the other side of the brick. I cleaned off all the mortar with a hammer and chisel quite easily.

My question is-
How long does the mortar take to make a strong joint?

I waited about 4 days before trying to set my next course. Everyday I noticed the mortar was getting harder but I could still scrap mortar off the sides of the bricks with my fingernail if I tried hard.

Could it be my technique. I soaked the bricks for 30 seconds. Made a peanut butter mix. I also dipped the brick real quick before buttering , then I set the brick and tapped it with a rubber mallet into place.

Some thoughts are-
• Maybe I should not have dipped the brick then put mortar immediately on the brick.
• Maybe I should not be tapping the bricks into place with mallet, this may break the bond
• Maybe I should not use an old bag of Portland I had laying around


I removed all the first course and since I had the mortar mixed (this time using new portland) and some more sailor bricks cut, I dipped the brick super quick, wiped it with a sponge, buttered just the brick in my hand and placed it. I did continue tapping the brick with a mallet, I like seeing the mortar ooze out the joint, maybe this is not making a strong bond.

Is there a test I can do on my sailor course to tell if the joints have bonded before I start laying more bricks?

•Do I need to butter both surfaces that go together or only on surface?

Does everyone who use the Homebrew mortar mix feel like they could go out and give one of their bricks a slight yanks after a day or two and feel confident the the joint is strong OR does it take about a week before the mortar is strong and set-up?

I have read every post that I could find about the Homebrew mortar but haven't found anything to cure my Mortar Anxiety.

Thanks your patience!

[Bread]

I forgot to say I am using #30 silica sand in my Homebrew mix. Not sure that matters.

[UtahBeehiver]

You answered you own question, old portland will not set, the moisture in the air finds it way into the bags over time and makes it useless. FYI, three sailors would make the side walls quite high, see attached pic. and would require some type of buttressing to support the outward pressure from the dome.

[david s]

Given that the base of a dome is the weakest part of the form, cracks nearly always start from the base, therefore long vertical joints are asking for problems in one course of sailors let alone three. Sailors are thinner than soldiers which further exacerbated the problem. Brick ovens are generally 4' thick. Laid on edge, only 3" thick is not considered strong enough because of the reduced thickness of the mortar joints. If you proceed with this design, please report back in a couple of years time as to its structural integrity.

[Bread]

Sorry Utah and Dave for the incorrect word use. I am stacking "stretchers" (flat half bricks stacked three high), Two of those courses are above the floor.

Its been 24 hours since I laid my second attempt on my first course. I can use my finger and scrape scrape the excess mortar of the butt end of my half bricks fairly easy although the joints seem to be hard. Is this normal, do I need to be patient and let it dry more? I tried lifting straight up (minor force) on a second course start brick that I placed yesterday and it seemed solid. I didn't want to lift any more and break any joints. I just can't tell if I should continue upwards and onwards until I feel confident with my bricks bonding.

I talked to a mason store manager. He said he never heard of such a home-brew mortar. He did say I should use mason sand for the sand mixture for strength. Maybe I will make up a couple batches, one for the tight joints on the face bricks and the mason sand to fill in the back gaps.

The manager also suggested that when I dipped the brick right before I buttered it there was standing water on the bricks and that the bricks face could not have the hydraulic effect that it needs to bond. He also said that I could use a rubber mallet to lightly tap the bricks in place and I have more than a few seconds to mess with the bricks as long as I am not picking them up or sliding or moving them inches. So hitting them until the mortar squeezes out from the joints is ok.

I want to tell myself that everything will be ok and I should continue but I would think the mortar would be hard and sticking to everything in a 24hr period.

[david s]

The bricks can be damp but not wet on the surface. Your cement, being old might not be working. Lime does have a retarding effect on setting time with Portland cement. Do you have the right lime? It should be builders lime (hydrated). What kind of powdered clay are you using? What is the ambient temperature range currently in your location?

[Bread]

After I removed my first course bricks because of a bond issue, I mixed up a new Homebrew with new Portland and re-layed the first course using new bricks as well. I quickly dipped each brick in a clean bucket of water and wiped off the bricks with a sponge.

I am using a Hydrated lime type S. I am using Lincoln Fireclay. It is in the high 50's with lots of rain currently. The lows have been in the mid 40's. That is probably the perfect temp for mortar to take its time setting up. I just want to get the bricks laid before snow season (which will probably be here next week!)

[CarlN]

Saw this post from last year. Did you figure out an answer for your questions? I'm just starting, got 2 courses done. Using home brew 3:1:1:1. Seems like it flakes apart easily the next day with a touch of my finger nail. I'm using all the correct ingredients from what I've read in all the posts. Fine blasting sand, Hydrated type S lime, Portland cement type I/II and Cedar Heights air floated fire clay. Mixed to a peanut butter texture. Should I not be using such a fine sand? It's really fine, for sand blasting. Am I correct is assuming the home brew doesn't fully harden till you cure the oven? How hard does it feel after a few days? Should it feel like regular cement hard or is it still kind of flaky when scraped with finger nail? I was also having bonding issues, I think I was over soaking the bricks. Stopped doing that and it seemed to help. Just wondering if it's all going to fall apart with one good wack? I too am having Mortar Anxiety. Seems like I can take a brick out with not much effort. Any advice would be appreciated.
Thanks to all the members for the overwhelming amount of information on this site!

[Gulf]

Cooler weather can add to the set time and also the curing time of portland based mortar. Also, fresh layed mortar should not be allowed to freeze. Portland will create it's own heat to an extent, but it is best if the mortar joints are allowed to set and cure in a warm/moist enviroment. The portland in homebrew is only in the recipe to allow for a faster set time. The portland will degrade over subsequent firings. What is key to the recipe is the clay and lime. Clay and lime react together to form a cementious type bond that will last for the long term. But, that bond is not over night. The potland in the mortar may take up to 28 days to get to full cure strength.

Sand blasting "sand" may not be actually a true sand. There are many different materials used for blasting media and it is above my paygrade to advise about it's use in homebrew other than to say don't use it. There are too many cheap and readily available sources for sand.

[CarlN]

Thanks Gulf, it’s been 3 days since I laid my first brick. Feeling a little better about the brew. It’s feels like it’s hardening like cement should. I can no longer easily scrape it with my nail. As far as the blasting sand, it says on the bag it’s fine sand washed, kiln dried, and screened. It appears smaller than a grain of sugar. Got it from a masonry supply place near me. They had other sand, this was the finest one. I’ll go get a different one just in case. Like you said, it’s cheap.
Thanks for the quick response.