Laying down mortar

[Hendo]

Re: Laying down mortar

A huge part of laying fire brick is to get the moisture in the mud and the brick just right. Although for the new oven I will use a true refractory mortar ...

I can?t agree more! I?m using a pre-mixed refractory mortar, so all I can play with is the moisture content of the bricks. And it certainly makes a huge difference, not only to the rate of setup, but also to the plasticity, stickability and workability (all technical terms here!) of laying these things. And when you?re limited by a 2-3mm max thickness, if things aren?t spot on, the mortar is dry before you even place the brick!

So far, I?ve found the best method is to lightly spray the brick bed, using a small spray bottle, quickly dunk a DRY brick into a pail of water ? just in and out ? and thinly butter all four sides (two on the bed and two on the brick being placed). This gives me enough time to quickly rub or tap the brick into position before it sets up, which is usually within a minute or two. While it?s setting up, I have to clean up the inside face immediately, or risk having to scrape off dry mortar.

I?ve tried soaking the bricks, and they take days to go off thoroughly ? I knocked one out once accidentally, and although dry around the perimeter of the mortar joint, it was like plasticine in the middle, and this was two full days after laying it! So every time I cut another course of tapers with the wet saw, I leave the bricks for at least two days to dry out. Too wet bricks also seem to cause the mortar to go powdery in time, which frankly scares me. Hopefully it?s only the outside edge.

My brickie showed me how he does it, and he had a different approach. He didn?t wet the bricks at all, but placed the mortar as he would a conventional brick wall ? very thickly and just on the bed and the ?butt? face of the brick. Then he pounded hell out of it to reduce the mortar thickness to that required. Fine until some previously laid bricks started popping out due to the tapers! They have set up well though, and the mortar remained workable for far longer.

All very different from Dave?s mortar, which sounds much simpler for the novice. But it still comes back to experimenting to find that ?one best way?.

I hope to have mastered the process by the last ring of the dome!

Cheers, Paul.

[Unofornaio]

Re: Laying down mortar

Id say defiantly stick with what you have been using. If you switch you may have different expansion issues and after all I assume many ovens have been built here with great results using that recipe.Your ok just play with the water content of the bricks and the mud. You should be able to get it so when you set the brick hold it for a short count and it should stay.

Putting a nice layer of sand on the hearth floor will catch any mortar..and what ever else falls..Im sure everyone here has had them fall at one time or another. Heck I did a firebox rebuild about a year ago and had some fall at first. I don't think I have built a fireplace in years, nobody wants them and you simply cannot beat the price of a prefab metal one..Im gonna build one here at the house because I just like the look of them and I cannot justify being a mason and not having a fireplace..I think its in the code of ethics somewhere..

[Les]

Re: Laying down mortar

Guy's

I've been working with the Forno receipt and find that it's a pretty good mix - granted it hasn't stood the test of fire yet The heat stop I was using had to be shipped (crazy expensive) and I find the two pretty similar. In fact, the Forno flavor allowed me to pull my shims quicker. The lime does add a workability factor, but I never seen that as an issue (until you clean the tools).

Les...

[asudavew]

Re: Laying down mortar

6 2 1

I wish I would of know this sooner............


Should I finish with this formula or continue with the one I have been using?

BTW. I hate the lime... Nasty stuff... I would love to avoid it!



Thanks guys!

[Unofornaio]

Re: Laying down mortar

Thanks guys I found it. Here is my thing with that mixture. Lime in mortar really only serves a workability function as in water retention to increase board life and stickiness. I don't see any need for it AND fire clay. Fire clay adds both these elements to mortar and while you can use SOME fire clay in place of lime for brick laying (never as full a replacement for lime) we have always used lime and never used it for heat applications. Interesting..

I'm not saying its is a bad mix just different and I would assume VERY VERY sticky. What we have always used is 6 sand 2 cement and 1 fire clay and this is more than sticky enough. My dad and I built my bakery oven with this mixture and I never had a problem. As a matter of fact when I dismantled the bakery oven (in use for 5 years) this summer I had to use a rotor hammer to get the chamber down and Id say about 70% of the brick broke in the field and not at the bond which to me was surprising. The other 30% were probably the ones I laid my father is a true master. A huge part of laying fire brick is to get the moisture in the mud and the brick just right. Although for the new oven I will use a true refractory mortar and this oven will serve double duty as my tomb because I am NOT taking another one down.

I remember a post now with that recipe being suggested by a furnace builder or something like that somewhere. It would be interesting to know the rational behind the lime addition.

Anyway Dave you are going to have to play with the mix to get it right to hold the brick and not slide off, I'm sure you will be just fine. And you can always use forms or sand there certainly is no shame whatsoever doing it this way.

[Dutchoven]

Re: Laying down mortar

FYI guys! Uno is right on. With that mixture it is important to be able to adjust for your particilar working conditions to make it workable. It took a lot for me to get the hang of it. Some mortar recipes would increase the sand to 4 or 5 parts as well.
Best
Dutch

[asudavew]

Re: Laying down mortar

Yeah,

Just about the last page.

[Hendo]

Re: Laying down mortar

Appendix 6 - p67 on mine!

[Unofornaio]

Re: Laying down mortar

Dave- I just looked over the plans and I cant find a recipe for mortar anywhere, except for the hearth bricks. Do you or anybody know what page?

[asudavew]

Re: Laying down mortar

straight off the plans... i believe

i dont have a copy at home

[Unofornaio]

Re: Laying down mortar

I don't know where this mix came from but with equal amounts of cement lime and fire-clay if your bricks are not sticking then your mix is too wet or the bricks are too wet. With that ratio how the heck do you get it off the trowel and on to the brick? Where did this come from?

[asudavew]

Re: Laying down mortar

Asuda
You just have to find the right balance between the stickiness of the mortar and the wetness of the bricks...could give the bricks less time to soak. What kind of mortar recipe are you using? 3:1:1:1 sand:cement:lime:fireclay? Could add a bit more lime?
Best
Dutch
P.S. Your oven is looking good!

Yeah, 3-1-1-1

How much extra lime should I add?
I am fixing to start the 5th course past the soldier course, and the angel of the dangel.....
I did cut my bricks into thirds .... maybe that will help.

And thanks for the compliment! I've been doing my best on a budget.

[Dutchoven]

Re: Laying down mortar

Asuda
You just have to find the right balance between the stickiness of the mortar and the wetness of the bricks...could give the bricks less time to soak. What kind of mortar recipe are you using? 3:1:1:1 sand:cement:lime:fireclay? Could add a bit more lime?
Best
Dutch
P.S. Your oven is looking good!

[asudavew]

Re: Laying down mortar

After I got the hang of placing bricks right the first time, it was a nice feature to hold it in place for a few seconds and move on to the next brick.
Christo

I bet that it is nice to have them hold in place. Maybe I should of went this route...I'm using cheap-guy mortar, and it takes quite a while for it to set up.

I'm fixing to move on to some upper courses where the angles might start to get me.....I can here them hitting the oven floor now.


Might be time for some sticks to hold em up.

[christo]

Re: Laying down mortar

The refrax firms up quickly. It was frustrating at first as I was so slow....

Soaking the bricks before use is important. Makes a world of difference.

After I got the hang of placing bricks right the first time, it was a nice feature to hold it in place for a few seconds and move on to the next brick.

Christo