New stove: Too much moisture ?

I bought the Annex6-RMHeater book & Rocket Mass Heaters by Ianto Evans & Leslie Jackson book and have studied them & I have tried to go by the books. Everything thing looked and worked great, great draw, etc. but I am getting massive amounts of moisture during the dying out burns. Is this normal? I am burning dry pieces of cedar. Long and thin. (2"X1/2"X2') The drum can is rusting internally and the clean outs are dripping profusely. I know there is moisture in the clay stabilized pearlite around the heat riser. I have only fired it up a few times to speed up the drying. I am still in the process of making it all. It takes time. This is my first, but I am trying to get it right the first time around. It is a 6 inch system, burn tunnel & heat riser is all fire brick, clay stabilized pearlite around the riser, 2"gap at top. My ducting in the bench is only 18'.

Robert Pritchard : Can you look on your Bag of Perlite, and see if by chance it says Horticurtural Grade Perlite ? If that has happened you will have to keep a eye on
things. You may get some settling around your Heat Riser as it finally dries out !

If you do not get your perlite to say it is Horticultual, or Ag perlite you could make a small adjustment to your Heat Riser to Barrel Gap closing it half an inch (.5'') just
with a small rounded cap of Perlite/ Clay slip ! this will raise the amount of heat you are radiating off at the barrel ! This can be a temporary Change !

If you can stand to wait, dont add any more cob until we see what actually is happening with your build! Post back with any more relevant information you can think of!

For the Good of the Craft ! Be safe, keep warm ! As always, comments and questions are solicited and welcome ! PYRO - LOGICALLY Big AL

Thank you for getting back to me!!
Yes it looks like it is Horticurtural Grade Perlite. Kind of fine. Sorry everything here is in Japanese. Each time I`ve done a burn the top of the barrel will come to max 350 f. I did put a layer of cob (sand/clay) on top of the heat riser to cover the perlite. I also packed the perlite clay mix quite tight around the HR. It is easy for me to open & inspect the top for checking. I could easily add more to the top to close it up a bit but I do want much of the heat to build up in the battery. But is this normal to get a lot of moisture for the first while?

Robert Pritchard : I know a Guy who - With over 17,000 members someone is going through what you are going through right now ! Horticultural Perlite is alleged
(by Rocket Mass Heater Builders ) to be the floor sweepings, however, remember that the ability to be super water absorbent is a large plus when it is mixed with
marginal dirt to put inside a flower pot

Damn it's like 8a.m and the start of my tomorrow there , right ?! It Kind of blows my m-ind !
I need to hook you up with another new builder who can only get Horticultural Perlite, so the two of you can talk, he wants to use a stiff wire mesh to contain the
perlite / Clay slip he wants to wrap around his Fire brick centered Heat Riser !

For the good - - -Your comments/questions will be answer'd Think like fire, Flow like Gas - - -PYRO - AL !

Robert Pritchard : The fellow member I talked about earier is Karl Meisenbach, His familiar to you, but unique to him crisis is the fact that he wants to use the only grade
of perlite that he can get !

If the two of you can get together and compare notes, we, the whole Rocket Stoves / Rocket Mass Heaters Membership may gain specific and useful information !

For the Good of the Craft ! Be safe, all comments,questions solicited and Welcome ! PYRO - Logic (Big AL)ly !

It looks like the moisture is stopping. I believe that I may have used too much water in the clay sip when I made the insulation around the heat riser. It is hard as a rock & dry inside the drum can now. I fired it up tonight & only a little moisture came out of one of the clean outs. I think I may need to increase the gap because the battery isn't getting wormed up like I wish.

Robert, is your mass dried up yet?

Can take three weeks before it's dried completely.

Hi Robert,

My name is Karl Meisenbach and Ive been posting separately regarding horticultural perlite as a heat riser insulator. Allen Lumley has mentioned you to me and how youre experiencing some issues around it. Some sources say it works while others say the opposite.

What has your experience been? I plan to mix it with clay slip and contain it within a fence wire around the heat riser. I, like you, want to get it right the first time so its been slow building for me..

Any advice on using horticulture perlite?

Hi Karl,
I don't see anything wrong with this kind of perlite I think that maybe I put a lot of water in it so it's taking time to steam itself out. I have been taking pics every step of the way, I could send you lots of pictures if you want. Here in Japan they don't really have much choice in handyman supplies, when one of my sons moved back to the States he was very very surprised to see what they have there compared to here. I have built many things in my life but this is a first and it really takes time & patients. So far I have only done burn times of 1 hour each day. The battery is not getting very heated up at all. Although the cleanouts are warm to the touch. I also have to cover it up each night as my 2 cats thing it's a new litter box. I haven't gotten to the straw cob yet. But getting there soon.

New litter box..thats funny..ill have to keep an eye on my cats then..

I have a similar situation in Uruguay regarding availability of materials. All i can get is horticultural perlite and i guess ill have to put less water into the clay slip. Another question, when insulating the burn tunnel, do i just mix perlite in with the cob or do i make an internal layer of perlite surrounded then by a layer of cob?

I would love to see the fotos if its not too much trouble and im assuming that your battery will heat up once eveything is dry and youre able to have a long fire going..hopefully it will be worth all the waiting. Are you using galvanized metal around the heat riser insulation? Whats your take on galvanized, is it toxic like some say?

Tomorrow i plan to make clay slip and begin tinkering with insulating the heat riser. I bought wire mesh to hold it in and am hoping that it wont fail at least in time for the perlite/clay to harden. Any thoughts?

Im also taking fotos along the way and hope to be successful in all of this so i can share the images proudly!

Sorry for getting back to you so late. Busy. I just mixed the perlite into the clay sip to make it stick together when you make a ball, but breaks when you squeeze it. That is what I did around the heat riser. I used the galvanized pipe because that is what was available. I would send you more pictures but it seems we can only upload 3 pics on this site. If you want, I can send some to your email directly from my email. I still am getting quite a bit of moisture coming out of one of the clean-outs. My living room is wood flooring so I cut the area out, it is concrete below my house, but for air flow I laid down cinder blocks & built on that. Yesterday I extended the external ducting & did a test burn & I got a lot of smoke back. So I will just stick to a short duck outside. My burn tunnel is 52cm & the heat riser is 120cm, so I think I have good draft. I'm working 2 jobs so as you can guess I don't have a lot of time to burn it each day to dry it out. Still haven't finished the cob, much less the cob with straw, then the plaster.

Great question and discussion.
Yes, it's definitely normal to get excessive moisture while drying out the system. Evaporation takes energy, cools the fire and exhaust faster, and then you get condensation in the pipes further down.
Glad to hear you are seeing things dry out a bit.

The dampness of the perlite is definitely a factor. Whenever insulation has water content, or in the case of refractories we also have the starch binder, it's common to see excess steam, soot, etc. during the initial firing-in.

When working in a building that's vulnerable to moisture, it can be helpful to proceed more slowly with adding damp material. For the thermal mass, we like to build up about 6" of cob thermal mass at a time, square and level like a course of adobe, with lots of holes poked into it to alleviate cracking and speed drying. Burn the heater for several hours and/or use fans to encourage fast drying. When that course is very dry and hard, add the next course, and repeat. This means you'll do a little work a few days apart over about a week, instead of trying to build the whole mass in one day.

When the whole mass is damp from the core out, it can take several weeks to dry. the moisture often oozes out near the bottom, which can stain nearby woodwork or encourage mold. Ventilate well with fans or passive air movement (open doors and windows for cross-breeze).

In most of our builds in conventional buildings, we try to include a semi-dry-stacked bottom layer so that there's some air movement / dryness at the very bottom. may be too late for your build, but useful for others reading ahead.

Yours,
Erica W

Hi Erica, great to have your expertise on this one..

When putting together the bench, its ok then to allow each course of cob to dry completely before adding the next course? I just want to make sure of that to avoid any problems..

Should i spray some water on the previous course before adding the next or just lay it on without any prep?

hi Karl yes its OK to let the prior course dry completely. and yes when you start working on it again you want to wet it and slip it so you get a really good bond. it also works to make sure your later courses are keyed into those holes to make a mechanical bond as well as a material bond.

2 for 1!! Thanks Ernie!!

These are some very good suggestions. Thanks.

A few new pics.