perlite

I am new to this forum and to this type of heating but am convinced that this is the way I want to go. I have ordered the books and videos and am collecting my materials so that when the plans arrive, I'll be ready to work. I am having a hard time in locating the fire clay and the right type of perlite. I have tried all the hardware and lumber yards for the perlite with no luck. Can someone suggest where to look for these items? I do have a company that makes firebricks 43 miles from me, but not sure they would sell me the powdered fire clay and have not contacted them since they are a commercial company. I did find firebricks at one of the local stores on the clearance isle for $10.00 per box of 6 and bought all the boxes they had, so I lucked out there, at least I hope I did. What would be better for building the heat riser, the firebricks or the perlite/fire clay mix? And do I have to use fire clay in the heat riser or is it just plain clay?  And if so, how thick is the heat riser walls if I'm going with a 6"system.  I also need to know if I have to use a 55 gal. drum for my manifold over my heat riser or can I go with a bell system made from clay bricks?  On the clay, can I use bentonite clay which is what plain kitty litter is, since my ground is already frozen here in Kansas? I read on one of the threads that rock has more insulating value than clay, so can I use that as the fill under my pipes then a layer of clay on top? I definitely will appreciate your time and effort in steering me in the right direction so I can be successful in this venture. Sorry for all the questions, I'm just very excited and anxious to learn more on becoming more self sufficient and getting started on this beneficial project.
Thanks in advance for the advice,
Loretta

Perlite is normally sold by garden or hydroponic shops where I live.

Welcome Loretta!
You have a lot of questions that will be answered by Ernie and Erica's book if you have that on the way. If you don't, I highly recommend it. I'll try to hit a few of your major questions.
While the price on your fire brick is a really good deal, I believe what you found are the type of fire brick that is not suitable for a RMH. If they are this type of brick, they will melt with the heat in a RMH. I've done it in a 5" j-tube dry stack test. What you need is a clay fire brick. I found mine at a masonry block supplier. They should come in fulls an splits and not look like cemented styrofoam. They will be heavy.

As for locating Perlite, most big box stores will have one or two large bags on hand. I typically get mine at Home Depot in a large, 2 cubic foot bag for $18-$20 a bag.

No, the 55 gallon drum is not mandatory. Masonry bells and bench's have been used quite successfully.

Hi Loretta; Welcome to Permies!
Your heading in the right direction! A RMH is simply the best way to heat your home.

Ordering the books and videos , and studying them will answer most of the questions you might have.

Can you tell us  what the wintertime temps might be?

So on to your questions.
Perlite is commonly found at nursery/ landscaping/ gardening stores. usually comes in a 4 cubic foot bag cost is 20-30 $ I believe I have seen it at home depot in 2' bags .
Fireclay will be found at a masonry supply store.  If they sell rocks ,then they will sell bricks as well, if they sell bricks they will sell fireclay.  A 50# sack of fireclay should cost from $6-14 each.
I bought two bags yesterday for $12.50 at Mutual Materials in Missoula, I have bought it at White block in Spokane as well. Both those are large company's who might have a branch near you.
Can you tell me what size and thickness the firebricks you bought are?  I am hoping they are 1 1/4" thick. That would make them a split brick, a very desirable thing to have.
If you can afford it ceramic fiber blanket is now the best thing to make a riser from. Ceramic fiber boards are being used for cores and to top off brick bells.If you can't afford ceramic products then.
Split firebricks can be used for risers, insulated firebricks are better.  A fireclay perlite riser (walker style) is also a good choice. I still use one in my green house rmh and it works great! Yes you need fireclay in the riser. Riser wall's are a minimum of 2" thick.
No, you do not have to use a barrel for a manifold. A brick bell is fine.
kitty litter clay is not a good choice.
You want lots of rock.,And you will find fireclay

Loretta Stuber wrote: What would be better for building the heat riser, the firebricks or the perlite/fire clay mix? And do I have to use fire clay in the heat riser or is it just plain clay?

Personal preference mostly. Bricks rob heat from the fire at first making it longer to get up to real rockety clean burning temperatures, but then hold onto it later for a much easier startup - no need to prime. The perlite/clay riser is considered mostly insulative so it gets up to temps faster but obviously doesn't hold onto it for very long. Also being much lighter, if need be, you can lift this riser off the burn tunnel for cleaning,repairing or replacing. I used just regular clay for mine but I'm sure either will do. Its the cheapest more DIY way to go.....and there also is a third option you havn't mentioned is what is called the 5 minute riser invented by a fellow named Pinhead - A chimney pipe lined with fiber blanket. As simple as it gets but its pricey. Much praise has been written on it lately. Maybe something to check out?

Loretta Stuber wrote:And if so, how thick is the heat riser walls if I'm going with a 6"system.

I think 3-4" is the recommended thickness....

Loretta Stuber wrote:I also need to know if I have to use a 55 gal. drum for my manifold over my heat riser or can I go with a bell system made from clay bricks?

Again, personal preference. Depends on how much you want instant radiant heat vs storage heat. I have always used a bare metal barrel but I remember hearing often that if you cover too much of your barrel with too much mass you won't have a high enough temperature differential between the inside vs outside of the riser (which gives it the rockety draw you need to help push the gasses through your system) your system could slow down or even stall. If your external chimney is giving you enough draft though, this may not be a problem. Others who have more experience may want to add or correct me on this.

Loretta Stuber wrote:On the clay, can I use bentonite clay which is what plain kitty litter is, since my ground is already frozen here in Kansas?

I have read that kitty litter is not what you want. Can't remember exactly why at the moment...

Loretta Stuber wrote: I read on one of the threads that rock has more insulating value than clay, so can I use that as the fill under my pipes then a layer of clay on top?

I think you mean rock has more storage capacity than clay. Therefore you want to use as much rock (or other hard heavy/dense stuff) buried in your mass with only enough cob needed to bind it all together....or you could go with a bell/heat stratification system instead.

Loretta Stuber wrote:I definitely will appreciate your time and effort in steering me in the right direction so I can be successful in this venture. Sorry for all the questions, I'm just very excited and anxious to learn more on becoming more self sufficient and getting started on this beneficial project.
Thanks in advance for the advice,
Loretta

Even after 5 years of tinkering with mine, I still get excited to learn new things and meet some wonderful people!  Good luck with your build!

Bentonite clay (clumping kitty litter) is not what you want because it is a swelling clay and thus has a HUGE water demand.  It takes many times the clay’s weight in water to make it workable, and then when it dries you get LOTS of shrinkage and cracking, and a weak structure in what hasn’t cracked.

 I found Lincoln 60 fire clay at a pottery supply store when getting higher alumina clay for geopolymer refractory experiments.  Another possible source would be masonry supply stores.

 What part of the world are you in?  We may be able to help find local suppliers with that information.

Also, for anyone wondering about workability and material properties of any commercial clay and many other minerals used in pottery, an excellent online database exists called digital fire

Here is their page on Lincoln 60 fire clay

https://digitalfire.com/4sight/material/lincoln_60_fireclay_971.html

Though much of it deals with the properties of Lincoln 60 as used (and fired to ultra high temps) in pottery, this paragraph in particular describes some of the properties that make it good UNFIRED for cob and clay slip and other areas in Rocket stoves and mass heaters.

“Lincoln clay has several other very unusual properties also:
-It has excellent drying properties (resistance to cracking) even though it has high plasticity. It's drying shrinkage is below 6%.
-It is very plastic like a ball clay yet it feels like a kaolin (it is not sticky as are other clays of the same plasticity).
-27% water is required to make the Lincoln clay plastic enough to work for pottery (whereas a typical plastic pottery clay body is 20-22%). Yet it still has a fairly low during shrinkage! This is very unusual.”
[In that second to last sentence I believe they meant “still has a fairly low DRYING shrinkage”

Anyone wanting information on materials that may be used in pottery, should google “digital fire #productname” to view mineral/elemental content information, and other material properties, such as water demand, plasticity, and drying shrinkage, that may be pertinent to it’s use.

Thanks everyone for their input & great advice, however, I'm a bit confused on some of it. I read on this forum that plain kitty litter was an ok sub for the clay in the bench when mixed with sand. I'm talking about the plain jane litter with no additives. I do have lots of clay on my 2 acres, just not sure if I can get to it at this time of year. Another point of confusion is the perlite. It has been said not to use horticultural perlite in the heat riser, only use the perlite insulation that blocklayers or masons use for block fill, so which is correct? Our temps aren't like Montana's. We range anywhere between negative teens unless we are having a blizzard then I'd say -20°F. The wind chills are what gets me since I have no wind break. I will try to find the Lincoln 60 fire clay at the suggested locations. I live about 62 miles from Wichita, Kansas. My goal is to lower my electric bill & keep my money in my pocket and it would be nice to have heat when the electricity goes out. Another question I have is about the duct that makes the run through the bench. Is it Hvac or stove pipe? I know that Hvac ducting is cheaper by far but isn't it galvanized & doesn't that give off poisonous fumes when heated? Why would you use this type of ducting instead of black stove pipe and what are the pros & cons? Or does it matter? Sorry about all the questions, I'm like a sponge soaking up all this information.

To clarify temps here in southeast Kansas, highs right now between 30-50°F & lows have been 30s to single digits with us going negative a couple days during this last weeks blizzard with 86%  humidity. This year it has been colder earlier than years prior. We usually don't see these temps until late December through the 1st of March.

Loretta, you might be able to save more $$ by omitting the ducting in the mass storage all together.  Matt Walker, and Paul Wheaton have videos on using a stratification chamber instead of ducting.

The firebricks I purchased are 4.5"×9"×1.25" model #FBP6. They came 6 to a box & are sold for pizza ovens, stoves & outdoor furnaces. I believe they came in the same box I saw on several rocket mass heater videos I've viewed online. So will these work?

Hi Loretta;
You COULD use kitty litter if you are building an encased mass, (not a cob bench) say brick sided where your cob isn't showing and wont matter if it cracks or is unstable.  The down side is the large amount of water you will need to evaporate before your mass can heat up.  I really suggest you avoid using it.
Do you have a neighbor with a backhoe ? Lots of farmers have one. If winter isn't too far advanced then they could scoop you some clay.  Might talk to the county road crew , they may have a spot where the clay is exposed.
IF you do a sided bench/ not cob your amount of clay needed just dropped, as well as the quality and cleanliness of that clay.

Perlite)  Buy what you find. If you find a masonry supply looking for fireclay ,they may offer block fill perlite,  I have never used it... always bought the 4' sack at the landscaping store.

Your only an hour from Wichita, you will find a masonry supply.

Stove pipe) Use black steel to start thru your mass (1 stick) then switch to hvac in 5' length's. Use one more stick when you pop up out of your mass (high abrasion area) then back to hvac to your roof.  
 Yes galvanized gives off a bad gas the first time it gets hot, after that nothing.

Well, cost really isn't a factor, I like the warm bench idea & have already purchased black pipe which I think I maybe have mentioned. I'm also building on a wooden floor so I know I need to use clay bricks but what kind?, to raise my heater & is it 1/2" or 1/4" cement or hardiboard that I use on top of the bricks? Do I also put cement board down right on top of my floor then stack the bricks on top then another layer of cement board? I found red clay bricks at home depot & I'm assuming that I need the solid ones and not the ones with the holes in them? Forgive me, up till now I've only laid tile & cement block foundation.

Thanks Thomas, I'll look for a masonary supply store for the clay & buy the perlite at the garden center then. Can you tell me how much perlite I will need for my heat riser? How many bags? I'll heed your suggestion & nix the kitty litter idea. So should I take the black pipe back & exchage it out for Hvac? Or will it make any difference in the heating abilities of the stove? I guess what I'm asking, is why use Hvac?

Hi Loretta;  Yes common solid red clay brick from H.D. is good.  I would use 1/2" cement /hardy board. none on the floor but supported by your bricks.

If your not working on a tight budget I strongly suggest you investigate ceramic fiber boards and morgan superwool ceramic blanket.  They are the most recent improvement in rocket building.

Your amount of perlite needed will none or very little if you use C.F. products.

Use that black pipe at the start and when popping thru the bench and if you have enough go up to the roof with it.

What Graham has mentioned are also called bells , different method of heat movement , same end result  warm spot to sit.

There is SO much for you to learn ... keep asking questions !

It has been 5 years now since I cast a riser. I THINK... I used 1 four foot sack of perlite and 2 50# sacks of fireclay... But I was very green had no clue what I was doing... that riser is still in service today.
Having said that I will tell you that I personally for me ,will never build one again!  Morgan superwool a piece of regular stove pipe to stuff it in and WALA a five minute riser good to 2300 F..  Read some of my posts to learn about that.

We use the hvac because it is cheap !  The black steel is necessary at the start of your mass due to the higher temp's after that no need hvac is fine. You must be gentle and bed them with cob and surround them with cob before piling on the rock.

thomas rubino wrote:No hvac is normally not galvanized.  Yes galvanized gives off a bad gas the first time it gets hot, after that nothing.

Not sure if your thinking of something else Thomas (or maybe just a brain fart typo?), but all the HVAC pipe I know of IS galvanized.

https://www.homedepot.com/p/6-in-x-2-ft-Round-Metal-Duct-Pipe-BCP6X24/100172086

There are different types of clay kitty litter, and the non water soluble “already fired” kind could be used as aggregate like sand.  It may be made from Bentonite clay.  “Johnny Cat” is one of these “already fired” clay litters, and is also used to absorb oil from shop floors, and to increase traction in snowy conditions.  

 The clumping litters made of Bentonite are unfired clay, and become a slimy, sticky mess, when sufficiently wetted.  

 Other types of granular materials, like play sand, or non-quartz mason’s sand might be better in terms of mass... a bag of the Johnny cat litter is only 20 lbs or so, whereas a similar volume of rock sand is more like 60-70 lbs.   due to the air spaces in the kitty litter, it has less mass and more insulative value.

I wondered about the rock. I have seen several videos that pile in the base rock layer then add the pipe but I know that hvac is very easily dented so I will be gentle. I have read about the ceramic fiber blankets & will look into building my riser as you suggested. Where do I get those two items? Online or who carries them?

Loretta Stuber wrote:The firebricks I purchased are 4.5"×9"×1.25" model #FBP6. They came 6 to a box & are sold for pizza ovens, stoves & outdoor furnaces. I believe they came in the same box I saw on several rocket mass heater videos I've viewed online. So will these work?

Those are usually referred to as “splits” for the fact that they are 1/2 as thick as the standard size  (1-1/4” instead of 2-1/2”)

 They are a great size to have as they can be used in a j-tube for feed and burn tunnel, or a batch box for batch chamber, without having an excessive amount of uninsulated mass having to heat up before clean burn begins to occur.  People use them in risers as well, but best performance in these systems comes from having a lightweight, well insulated riser, best performance of all coming from ceramic fiber products or insulating fire brick, which is much lighter weight and less abrasion resistant than what you have

I originally was thinking of using the plain kitty litter as a sub for regular clay in my cob which is mixed with sand,  but y'all have convinced me that's not a good idea.

So if I go with the ceramic fiber blanket inside stove pipe for my heat riser,  then would I need the perlite?

Loretta; Gerry is 100 % correct,  my bad , hvac is galvanized . I was given old aluminum hvac when I built mine.  I wouldn't worry on using it though. The part about it only off gassing one time is true.  

I found my Morgan superwool on ebay .  There is two kinds of ceramic blanket a cheaper refractory blanket ,Hazardous like asbestos or  Non Refractory blanket , not hazardous.  There are several manufacturers , but I found that the superwool was easiest to locate ... its not free though ... It cost me $129 to get 12.5' .

Ceramic boards are also easily avalable on ebay.

Loretta Stuber wrote:I wondered about the rock. I have seen several videos that pile in the base rock layer then add the pipe but I know that hvac is very easily dented so I will be gentle. I have read about the ceramic fiber blankets & will look into building my riser as you suggested. Where do I get those two items? Online or who carries them?

Ceramic fiber blanket is available various places, one being wood stove home heating retailers, some people find it can also be salvaged from the body of a ceramic top cook stove at some appliance salvage yards.

 I bought a 48” x 100 foot roll of 1” thick, 8-lb per cubic foot density blanket for around $200, from Zoro.com, and see that it has risen to $220 since that time.  That is the cheapest I have found for Ceramic fiber blanket online... about $2.20 a square foot, delivered.  

 Also, I believe in reading since, that the 6lb/sq foot is actually more insulative for a given thickness (and $20 cheaper per 100 square foot roll to boot)

 I had no issues with this brand of CFB material in cutting and handling, but am not usually particularly bothered by most fiberglass insulation either, so cannot say if it is the “safer kind” that Thomas R espouses... but for you and anyone else who wants 8lb Unitherm CFB cuts from a 48” wide roll for risers and such, i’ll sell custom cuts off of it for 3.30 a square foot plus whatever shipping costs, if that turns out to be a way better price than you can get elsewhere.

Correction,  48” by 25 foot length roll of 1” thick, 8lb CFB... 100 square feet for $197 delivered, at the time!

Re: galvanized HVAC pipe

“When zinc is raised to a high temperature (at or above its boiling point around 900C), it burns and forms zinc oxide smoke.“

So pretty much anywhere after the barrel, galvanized should be fine...

 One can also use a plumbers torch or weed burner, or camp-fire to burn the zinc oxide off of hvac pipe outdoors, given an open area with no neighbors close enough to get fumigated, and keeping one’s self upwind of the offgassing of zinc oxide vapors.  When the area turns a dull grey color and no more smoke comes off of it, it is safe for high heat without creating fumes after that.

 When I did a 5 minute riser and only had galvanized on hand, I “burned it off” with a plumbers torch, and a squirrel cage blower fan placed to blow accross and through the pipe and carry the fumes away fast and dilute them to non hazardous levels quickly.  I didn’t do the camp fire option, because my neighbors are close enough that having that much zinc oxide fumes come off at once could expose others to hazardous levels if the smoke drifted toward their houses.

 I mitigated it by doing it slowly and creating instant dilution with the fan, as well as minimizing my own exposure.

 The other thing to keep in mind, with the CFB riser, is that it lines the INSIDE of your pipe or tube, so if using one inch thick CFB, and you System size (and riser inside diameter/system CSA) is 6”, you will need an 8” pipe section to get a 6” I.D. when lined with your blanket.

Hi Loretta,
 You are in good hands here!

I just wanted to throw out that I got a bag of Perlite off of Amazon. Free shipping and pretty cheap.  I later saw the same product at a local farm supply store.
I ordered the rockwool blanket on line as well.  I could give you the supplier if you want it.
I am lucky enough to have a Clay Art supply store within 10 miles of my house.  They sell Lincoln 60 Fire Clay.  Maybe there is a pottery studio or such in your area??

Welcome!
Staci

Hi Loretta;  You may still want a bag of perlite on hand, even if you do not use it.. Depending on how you build your rocket core and how you choose to cover it you may want  to make an insulating cob to surround your core.
If you  choose to surround the core with a larger brick box. You would want an insulating product in between, like fireclay /perlite mix, same mix you would use in a riser.
My mass has a stone wall behind it... I used cement board and spaced it out from the rock 4" then I poured loose perlite in to insulate. its pretty handy stuff.

Loretta;
What size rocket were you thinking of building ?
 About your split bricks. As long as they are the correct kind ,how many were you able to get ?
 I needed 16 to build an 8" feed tube... I bought 15 before I knew this... I went back and bought 3 more... good thing as I broke one during cutting. Have 1 new one left, but my feed tube is done.
 

I agree with Thomas, that an insulative perlite aggregate in cob, or as insulative fill, as in his "loose fill" example may be very useful in some areas of your stove, for instance, as in an insulative heat resistant layers around, and under your brick core, above the cement board that maintains the air gap for heat dissipation above the floor.

 You can make bench height bells out of barrels split in half vertically, connected at the ends with an entrance from your manifold and a low exit at your chimney, then bed cob around & over them with confidence they will support your weight.  Bells are generally superior to long ducts at heat extraction with MUCH less drag on the exhaust gas stream, allowing a larger heat extraction surface in a smaller footprint, and more even heat distribution over the entire bench/bell area.

Ok, I'm back:) I found the perlite at a garden center for $35 for 4 cu. ft. which seems a bit high. Can't get it at home depot here or anywhere near here:( I  also found the Lincoln 60 fireclay for $20 per 50#s or $30 per.100#s. They also have the ceramic fiber blanket for $7.50 sq. ft. So how much fireblanket would I need? And can I do better shopping online? I priced the Lincoln 60 fireclay online at $8.40 per 50#s but shipping for 2 bags was like $95. Nope, too much for me on the shipping. Are the prices I found in Wichita listed above about right considering I don't have to pay for shipping. Planning on looking for the fire blanket & board at fireplace & woodstove outlets. Nothings cheap but well, I'm finding out Kansas is quiet high compared to where some of you live, that's for sure. Anyway, your input will be much appreciated.

All of those do seem rather expensive.  

My question today is about the ceramic fiber lining in the stovepipe for the heat riser. Is this sandwiched between 2 pcs of pipe like the perlite/fireclay or does the fire burn up thru the insulation? If it is sandwiched between the 2 pieces of stovepipe, then why wouldn't triple wall insulated stainless stovepipe work for the riser since it already has the ceramic fiber insulation in it between 2 pieces of stainless stovepipe.

The CFB is rolled inside a metal or clay pipe and is directly exposed to the flame path.

If it's used to surround metal, the metal will rapidly decay under those conditions.

See https://permies.com/t/96986/Starting-testing-ceramic-fiber-chimney

Claudia,

  I have seen others using this method report that if you cut the blanket so it is a bit more than the circumference of the outer pipe, it will hold it’s self in against the side, so add an inch to the circumference on your initial cut width and trim it down from there until you have a good fit.  I have a test bed j-tube that has this type of riser and have run it for 10 hours or so full out with no issues or deterioration, and did not use any “fiber-rigidizer” sodium silicate solution.  (I believe the silicate solution also lowers the insulating value of the CF blanket as well)

 Better a half inch or inch wide than starting a little too narrow and having it loose and not self suspending.

 

Matthew, my name is Loretta not Claudia. Wasn't for sure if your post was addressing me or not & we all make mistakes.. on the heat riser built with ceramic fiber insulation, so what I'm seeing is just cut & roll a piece of the 1" ceramic fiber & slide into a piece of pipe, that's it. That seems to be the way to go. How big does the pipe need to be & the opening after you insert the ceramic fiber?

If you are building a 6" rmh , than you will need an 8" pipe , which you insert the 1" thick ceramic blanket into , ending up with a 6" riser.  
8" RMH and you need a 10" pipe.

A quick search for masonry supply's in Wichita and I found 3,  did you shop around at all ? $20 for fireclay is robbery. My tiny local hardware store sells it for $14.50 a sack , big supply house I pay $6.25 a sack

Loretta Stuber wrote:Matthew, my name is Loretta not Claudia.

 Yes, sorry Loretta, I think I fat fingered your name and my phone autocorrected that to a name that's in my contacts.

And yes, you roll it a bit smaller, and press it outward once slid into postion vertically (easier done with the metal pipe laying down tho) working up the length of it from each end, and should wind up with no gap at the vertical seam of the blanket liner, and enough pressure that the thing holds it's self in place... (doesn't take much pressure, but the blanket can't be short on that width for the circumference)

Good Morning Loretta;    Check this post out.       permies.com/t/95849/Working-Morgan-Superwool-ceramic-blanket

Thanks guys! Where are you located Thomas? Yes, I checked around & that was the cheapest place I found it, at a ceramic supply shop. None of the masonry supply stores carry it here. And ordering it online, well the clay is cheap but that shipping is a killer. Is $7.50 a sq. ft. for the ceramic fiber roll to high also? It's also at that ceramic supply shop. I'm assuming if I have a 36" riser I'd need the ceramic fiber insulation cut to 37"? And to fit in an 8" pipe, I'd cut it how wide? I'm not really good at figuring circumference measurements, don't want to come up short. I'll have to write that site down you shared Thomas, as it wasn't highlighted so can't just click it. But I'll view it today. Matthew, I definitely know about the auto correct on the phone, it happens to me alot, Lol! No worries, I'm good:)