Using Porland/Fireclay cement for a Chiminea?

[david s]

Re: Using Porland/Fireclay cement for a Chiminea?

The outside is bound to get some fine cracks fire it up and see how it goes. You could try a flexible acrylic render on the outside. Simply water it down so you can paint it on then give it several coats.With a chimea you want to try and avoid flames which will heat it up too fast and cause cracking. Better to stick to coals, heatbeads or charcoal.

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

David,

so, a couple of questions. (partly important for the howto i'm writing to give the next ovenistas some good tips)

- Do you (or anyone else who like to chip in ) think you could build a medium (one and a half foot diameter) structure from just 'refractory mortar' and a support structure like chickenwire? How much stronger (percentage wise) is 'pure' concrete (Portland & sand) compared to the refractory mortar mix? : ( from High Heat Primer

* 1 part Portland cement
* 3 parts sand
* 1 part lime
* 1 part fireclay

Is it more brittle than regular cement? Why would you and wouldn't you use it?


- You mention "flames which will heat it up too fast" and then say "Better to stick to coals, heatbeads or charcoal".

In my (subjective and scientifically unfounded experience) a coal or charcoal fire burns hotter then the boiler room in Hell while a small wood fire burn much more mellow. I am talking about charcoal that is 'burning' (being help with a stream of fresh oxided like the wind or upwards draft). I am mistaken and are wood fires hotter then coal? Why would a blacksmith use coal instead of wood?
__________________

[david s]

Re: Using Porland/Fireclay cement for a Chiminea?

I'm sure you could build a structure using the home brew ref mortar. It wil not be as strong as ferro cement though (whole boat hulls are sometimes built using this method.) Portland cement breaks down when it reaches 300C and that's where the lime takes over because it can handle the heat, but doesn't have the strength on cement. Lime is also good because it is slightly elastic and leaves the end product porous so moisture travels in and out more easily.
Sudden heat from direct flame impingement is likely to cause too rapid a rise in temp. possibly resulting in thermal shock failure (cracks) The blacksmith uses forced air (oxygen) to get the fire really hot. When I said coals I meant the gentle burning coals left after the flame of a wood fire.

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

It's done!

I have finished the constructing and fired the little devil a couple of times with much success.

A very extensive how-to, which much attention to material and construction considerations can be found on Instructables.com:

Outdoor fire place (Chimenea) from ferrocement

I hope you find the information useful and since I plan to build another, better version I am very eager to find any experiences of your... er, experiences here.

Matt

[david s]

Re: Using Porland/Fireclay cement for a Chiminea?

It looks fantastic. I would be very careful about firing it with flames coming out the chimney. You risk creating cracks. would love to know how it holds up after 20 firings.

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

Yes, the small ring of mortar around the base of the stove pipe has some small cracks in it, but I could not resist letting the flames shoot out the top to get a good photograph. ;-)

Won't be doing that on a regular basis, I think.

Interestingly enough the dark grey concrete is turning a terra-cotta like orange. I am not sure if it is the cement "baking" or the iron oxide rusting.

[david s]

Re: Using Porland/Fireclay cement for a Chiminea?

The playing with fire is so much fun. I can understand you wanting to give it a "real caning" It is like building a sports car. You just have to take it out on the road and open it up.

[cvdukes]

Re: Using Porland/Fireclay cement for a Chiminea?

Matt,
Congrats!...it looks great. I especially like the face. Do the eyes glow with heat for hours afterward?

One suggestion. You might want to put expanded metal or stucco underlayment wire over the openings on the chimney to keep sparks from flying off into the brush. I bought a few peices of wire mesh raingutter guard that I've worked into the tops of my chimneys 'cause I'm at the edge of the woods and hate to see it all go up. The gutter guard stuff is expanded aluminum but seems to hold up to the heat okay.

Oh, and how much did it end up costing you? Not counting the cost of the bandages for your hands (forgot to warn you about the sharp ends of the chicken wire, didn't I?).

Craig

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

Matt,
Congrats!...it looks great. I especially like the face. Do the eyes glow with heat for hours afterward?

Thanks! and no, unfortunatly the eyes behave rather unspectacularly at night, there is no light shining in them.

One suggestion. You might want to put expanded metal or stucco underlayment wire over the openings on the chimney to keep sparks from flying off into the brush. I bought a few peices of wire mesh raingutter guard that I've worked into the tops of my chimneys 'cause I'm at the edge of the woods and hate to see it all go up. The gutter guard stuff is expanded aluminum but seems to hold up to the heat okay.

That is a good idea, I could make it inside the chimney so you would not even see it.

Oh, and how much did it end up costing you? Not counting the cost of the bandages for your hands (forgot to warn you about the sharp ends of the chicken wire, didn't I?).

I list the costs on the Instrutable page. I reckon around NZ$150 + some tools as I don't have access to all my stuff. Main cost being the cement and chicken wire.

Glad you enjoyed it and thanks again for the helpful suggestions, they made all the difference.

Matt

[JulieKulak]

Re: Using Porland/Fireclay cement for a Chiminea?

Hi!
Great information. I was wondering if you could tell me how to keep the pattern of the burlap from embedding itself in the final wet concrete coat while it cures. I'm assisting an artist who is sculpting a whale (a big one!)from concrete. We're close to applying the final coat of concrete, but we can't figure out a way to cover/cure it without getting a texture or marks on the cement from the plastic. We thought about tents & scaffolding, but it seems that air circulates too much and dries teh cement too quickly with those methods. Any thoughts? Thank you! -Julie

[cvdukes]

Re: Using Porland/Fireclay cement for a Chiminea?

You can let concrete set up a little bit before covering with anything. Once it feels hard, it won't get the burlap impressions.

Reason for the covering is to strengthen as it cures. Full cure strength takes up to 28 days. Keeping it slightly moist for 3-5 days makes for stronger concrete.

[david s]

Re: Using Porland/Fireclay cement for a Chiminea?

I find cling wrap works well. Because the plastic is thin it has less tendency to mark the concrete. You can also get a complete seal more easily than thick plastic and it's easy to wrap around 3d forms.

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

You could also put a nozzle that produces a fine mist of water on a garden hose and aim it at the object.

[JulieKulak]

Re: Using Porland/Fireclay cement for a Chiminea?

Thanks a bunch for the suggestions. I ran them past the artist, and her concern was that letting it set until it's hard enough to cover would take hours. The head of the sculpture is approximately 10' high, at least 12' in diameter, so saran wrap is out We've thought about doing a wet cure with porous garden hoses that mist plants, but we're not sure if the mist would be even. I guess the difficult part of this whole process is that we have to get as much of the sculpture covered in concrete as the day allows, and still be able to let it cure properly without marks. Harder than it sounds!

[thijsatteiltje]

Re: Using Porland/Fireclay cement for a Chiminea?

My experience with any of these 'things-you're-not-quite-sure-of' is: try it out.

Do a test batch, approach it scientifically, make a couple of setups and see what works best. Definitely don't try something for the first time with the Magnum Opus of this artist. ;-)

(although first knee-jerk reaction would be: "it's concrete, bro. it's gonna look like concrete!" ;-)

Also, you could take angle grinder and a sand disc or metal brush to make a smooth finish I guess.

matt