36" in Seattle

[fxpose]

Re: 36" in Seattle

Wow, that's coming along beautifully! And I love the look of that arch.
I plan on using a center offset brick guide as well.

[kebwi]

Re: 36" in Seattle

Cut and mortared arch merges for the first curved course, thus completing that course. Phew!

Completely constructed the outer arch. This was the first (of three total) arches in which the last brick went in without a shave. I don't say keystone b/c in the case of one of the three arches, the center line was a mortar gap, thus that arch had no keystone. Just saying...

Notice that I was able to build the outer arch with only a few major mortars due to having built most of it in sections already. For example, the first photo represents a single mortar job on-site, since those four bricks came as a block from the basement. Likewise for the four just-off-center bricks on either side of the keystone. Earlier posts (and photos) make it clear what I'm getting at.

BTW, the dark-light-dark-light-dark pattern on the outer arch isn't a mistake. Once I realized that the cut bricks were exhibiting so a wide range of color I figured I might as well take advantage of it.

I'm a tad disappointed that the mortar gaps on the outer arch are not consistent. They are the by-product of attempting to conform to the protractor during construction. Sometimes the previous brick was a little low and required a fat mortar gap to get the next brick back to the right position...but at least the keystone is tight, which is not just aesthetic, but also structurally important, since the keystone will bear most of the weight of the flue.

The last photo shows that I cut a two-thirds length corner off the highest full-depth brick. That was a last minute decision as I was investigating my design last night. I'm hoping it will somewhat alleviate the shear stress between the vent side-wall and that last brick, which being rather steep will not be a very good load-bearing joint. By cutting the vent side-wall to notch over that last brick I should be able to improve the situation a bit.

Cheers!

[jmhepworth]

Re: 36" in Seattle

This looks really good. Nice work.

[Dino_Pizza]

Re: 36" in Seattle

I really like the variation in brick color. Good job picking that up and using it. Your mortar joints look even and just fine to me. I'm really diggin' the fully arched entry and the angle you cut off those entry arch bricks.
Nice job, Dino

[kebwi]

Re: 36" in Seattle

There's something odd about these bricks. The darker ones are noticeably harder to saw through, and I believe (although I haven't measured this precisely) that they feel heavier. I would almost say I got a mix of fire bricks of varying grade, whether low/medium or medium/high I really don't know. The other thing is that the bricks aren't a clear mix of two or three types, but rather contain a smooth gradation of color and hardness. The place I purchased them from refers to them simply as medium-grade across the board.

I don't quite know what to make of it.

[david s]

Re: 36" in Seattle

Kebwi,
As clay has a high shrinkage rate, the more fireclay you add to your mortar will create more shrinkage. Don't overdo the fireclay content.

[kebwi]

Re: 36" in Seattle

Ohhhh, dammit. I've been asking about mortar recipes and increasing the fireclay for weeks on FB and no one would comment on the effects of more fireclay until now. I'll try a more conventional mix from now on. I see some followup posts from Lars (the originator of my mix) who admits his bricks sound hollow when he taps them...which to me not knowing anything about this topic, seems intuitively indicative of mortar shrinkage...unless I'm misinterpreting the cause of his "hollow" brick taps.

I must admit that one reason I felt a little emboldened about increasing the fireclay was that of the numerous recipes I had found scattered around FB, for the most part they had more fireclay than portland relative to the conventional Pompeii 3:1:1:1...but maybe that was all a mistake and 3:1:1:1 is really the right mix to use. (If I recall correctly there is actually a more precise ratio that is the true advocated ratio, but 3:1:1:1 was chosen purely for rememberability...but I'm not sure what thread that was in now.)

I'm moving forward too fast. So long as I didn't have a definitive answer to my mortar questions, I should have held off until I got the right information in hand. Instead I plowed ahead.

Thanks david s, I really appreciate the help.

[trockyh]

Re: 36" in Seattle

I must admit that one reason I felt a little emboldened about increasing the fireclay was that of the numerous recipes I had found scattered around FB, for the most part they had more fireclay than portland relative to the conventional Pompeii 3:1:1:1...but maybe that was all a mistake and 3:1:1:1 is really the right mix to use. (If I recall correctly there is actually a more precise ratio that is the true advocated ratio, but 3:1:1:1 was chosen purely for rememberability...but I'm not sure what thread that was in now.)



Thanks david s, I really appreciate the help.

Hi Keith,
I'm glad you are asking these questions, hopefully by the time I'm ready for mortar, it will be straight in my head. I'd love to just order the mortar from FB, but the cost might prevent me from doing it. Not working at the moment, I need to watch my pennies.

Tom

[tfasz]

Re: 36" in Seattle

Yes - I bought my bricks from the same place (I-XL Masonry | Showrooms - Redmond, WA) and have noticed the same thing. I decided to use the dark colored ones for the landing/entry and keep the light colors for the interior of the oven. I made a couple of different trips to pick them up and all of the pallets I saw had similar variety of shades. There must be some variation in the colors of the raw materials they use to make the bricks.

Nice work on getting the gradient in the arch - looking good.

[kebwi]

Re: 36" in Seattle

Hi Keith,
I'm glad you are asking these questions, hopefully by the time I'm ready for mortar, it will be straight in my head. I'd love to just order the mortar from FB, but the cost might prevent me from doing it. Not working at the moment, I need to watch my pennies.

Tom

From the countless testimonials on FB -- some several years old now and therefore representing well-established ovens -- I have full confidence that homebrew mortar works, and I have had no trouble mixing or otherwise working with it. I just like to understand how things work, so I like to ask questions like "What happens if you change this parameter?" Questions like that are pedantic and tiresome to a lot of people though, which I suspect is why I had such a hard time learning what effect increased fireclay would have.

If you're a novice like myself, I suggest following the prescribed 3:1:1:1 unless or until you have specific access to knowledge above and beyond the basic introduction. I read a few claims of modifications of the brew and thought I would try one of them (mostly b/c I didn't see any responses to that other mix that suggested it was a mistake)...but I probably should have left well enough alone. Now the lower courses and the arches of my oven will contain a higher proportion of fireclay than my my upper courses if I revert to 3:1:1:1. I don't know what that means for the properties of my oven.

.............probably not much though. It most likely won't have harmed or helped me in the long run.

Best of luck!

[kebwi]

Re: 36" in Seattle

Yes - I bought my bricks from the same place (I-XL Masonry | Showrooms - Redmond, WA) and have noticed the same thing. I decided to use the dark colored ones for the landing/entry and keep the light colors for the interior of the oven. I made a couple of different trips to pick them up and all of the pallets I saw had similar variety of shades. There must be some variation in the colors of the raw materials they use to make the bricks.

Nice work on getting the gradient in the arch - looking good.

Aside from appearances, do you also agree with me that the darker bricks are notably harder and perhaps imperceptibly heavier? I'm curious if they actually have different thermal characteristics (presumably higher heat capacity, hence longer heat up time but also longer heat retention).

[kebwi]

Re: 36" in Seattle

Not to dwell on this, but for informative purposes of future readers of this thread, here is another thread (started by myself no less) which contains multiple independent claims of various recipes which contain higher than 1:1 fireclay/portland. I'm not saying any of them are right or wrong or that recommendations to the contrary are right or wrong; I'm just pointing out how I got into the position of increasing the fireclay in my own mortar in the first place, for better or worse.

[cynon767]

Re: 36" in Seattle

For me, the increased fireclay hasn't been a problem thus far. I wanted to keep the portland content slightly lower than the basic formula on the theory that the final joint would be weaker once the portland burned out. I let the mortar have a long drying time before firing to cure, approximately 6 weeks of sitting while I worked on the other aspects of the project; it has not shown any sign of cracking, either during drying or in the heat curing. I think that, with the high clay content, this slow and steady process may be helping prevent cracks. Hard to test, but that's the premise I'm working on.

I always assumed that one of the reasons an equal part of lime is added to the homebrew recipe is to counteract the shrinkage of clay; Lime increases both stickiness and plasticity of the mortar, making a weaker bond with the bricks than porland but a joint which is more flexible and less prone to shrinkage cracking. It also doesn't break down at wfo temps like portland does.

I have done a little preliminary research on this, and am doing more now; I will post the results in the mortar thread.

[tfasz]

Re: 36" in Seattle

Aside from appearances, do you also agree with me that the darker bricks are notably harder and perhaps imperceptibly heavier?

Yes - they certainly are harder and I find I have to take it about twice as slow cutting them. They also seem to give off some sparks when cutting (even on the wet saw).

I had not really noticed a weight difference, so I threw some on my kitchen scale tonight and both the darker and lighter bricks all where in the 3.2-3.3 kg range. One of the light colored ones was the heaviest of the bunch.

[kebwi]

Re: 36" in Seattle

Interesting, so the perception of weight difference was purely psychological. I'll have to measure them myself. I have also noticed the sparks, although I hadn't noted that the darker bricks sparked more. I'm sure I will now that you mentioned it.

Ta.