I agree with your correlation of brittle rock and salt (DEF). My thoughts about overheating the rock were in context to the crystallization of salts within the rock during the baking process.

I think you're right. It's the lack of moisture, rather than excessive heat or duration of baking that causes the spalling.

I had the unfortunate honor of watching my neighbor cook some steaks out on his grill last night while working in my yard. He would take a pull off his beer, then open the grill, poke at the meat some and then liberally splash his beer (the same one he was drinking!?!) over the meat, close the lid and repeat. He was basting his steaks to provide moisture. This brought to mind images of rich, fat, naked guys sitting in saunas, ladling water over the hot lava rock, producing steam.
Besides being thoroughly disgusted, I had an idea for the BBQ crowd.
Might it be possible to make a foil (cookie sheet?) barrier between the flame and the rack, and ladle water onto this foil at really regular, short intervals, thereby providing more steam. Or do you think that would just let what steam there is, escape as the door is opened more often?
I'm not sure that this would provide better results then wrapping the rock in wet something another and foil, but it might be worth a try...

if using a BBQ to bake the rocks, I have an idea.

A college meal i used to cook was called "Beer Can Chicken". I fire up one side of the grill, and then place the whole chicken on the other side of the grill, out of direct heat.

the whole chicken would get seasoned, but the main gimmick is that I'd take a can of beer, drink half, and then poke holes in the beer can sides and proceed to stuff it up the chicken's butt and let the chicken sit on the beer can, upright, on the grill. Great recipe of you can walk away for 2 hours, by the way. extremely juicy chicken.

Anyway, why couldn't we put a metal pan with water over the flame on one side, and put the MMLR on the other? you'd avoid direct heat on the rock, and you'd have a place to keep a water pan for maintaining humidity.

maybe this is standard procedure, SOP, for baking MMLR this way. I've been keeping up but didn't see any/many entries for baking rock on a grill. good idea.

-G.

[QUOTE][i]<a href=showthread.php?s=&postid=10324396#post10324396 target=_blank>Originally posted</a> by goldmaniac [/i]
[B]Anyway, why couldn't we put a metal pan with water over the flame on one side, and put the MMLR on the other? you'd avoid direct heat on the rock, and you'd have a place to keep a water pan for maintaining humidity.[/b][/quote]
It sounds reasonable - if the issue isn't with the steam escaping from all the vents and uneven joins in the BBQ.

[quote][b]maybe this is standard procedure, SOP, for baking MMLR this way. I've been keeping up but didn't see any/many entries for baking rock on a grill. good idea.
[/B][/QUOTE]

I hate to sound uppity, lol - but I don't think there is a SOP for baking LR - I'm pretty sure that I am a ground-breaker in this area. Or if someone else out there has developed a working method, they haven't shared it online that I can find.
I did a lot of googling before trying this idea, and if I even found mentions of baking rock in any forums, usually it was followed up by a failure post, and you guessed it - all complained about friable rock...
And I think Spike is the first to post on the thread that he had actually used his BBQ - a few have talked about it, but nothing has been posted, so...

I just happened to see PRP Powder used on TV. It is very small air filled hollow spheres of beeswax. No idea how expensive it would be but it would seem like a alternative way to lighten rock and make it more porous without using salt. It is biodegradable so it would eventually all disappear and it's mostly air to start with. It's made by Universal Remediation, Inc. in Pittsburgh PA.

[QUOTE][i]<a href=showthread.php?s=&postid=10324396#post10324396 target=_blank>Originally posted</a> by goldmaniac [/i]
[B]if using a BBQ to bake the rocks, I have an idea.

Anyway, why couldn't we put a metal pan with water over the flame on one side, and put the MMLR on the other? you'd avoid direct heat on the rock, and you'd have a place to keep a water pan for maintaining humidity.

-G. [/B][/QUOTE]

I was going to suggest the same thing, a pan of water should last a long time before it would need to be refilled.

By the way I posted a while ago about my rocks that seemed to cure in about a week in tap water. Well it was true they are in my tank. I will try and get some pics tonight when I get home.

[QUOTE][i]<a href=showthread.php?s=&postid=10331730#post10331730 target=_blank>Originally posted</a> by johno4 [/i]
[B]By the way I posted a while ago about my rocks that seemed to cure in about a week in tap water. Well it was true they are in my tank. I will try and get some pics tonight when I get home. [/B][/QUOTE]

Interesting. You never answered the questions posted to you about these rocks, so more info would be appreciated. My memory says these are now around a month old, correct? That would be within the normal time-frame for using them.
But a one week cure/kure with traditional portland is not. A week hasn't even seen the hydration phase completed, unless using quick cement or baking.
I'd asked about materials used, your methods, etc. as well as asking if you were sure your pH test was accurate, but you didn't reply (or if you did I didn't see it). So I will ask again. :)

I went to the LFS to spend some of my birthday money, but to also take "Disco Dancing Rock" (my first perlcrete test) in and see what he thought of it.
He really liked it :)
I had just done the 3 day pH, in saltwater, and this 10/11? day old rock was stable at 8.5. I was just showing it to him, and mentioned that I needed to put it in a tank, and I was going to sacrifice my 10g bug tank but he snagged it and put it in the fish display. I'll get a pic of it when next I'm out that way. I'm curious if he plans on giving me the rock back after we see if it harms anything, lol.

Sorry for the delay with the response to your questions, I just got really busy.

rock was made using 3/1, sand/portland cement. The sand was kolorscape sand found in the garden center at Home Depot. I formed it in a sand mold like the traditional method in a styrofoam fish box. After 20 min. or so I poured a pitcher of water over the mold and covered the entire container in a garbage bag so no water got in or out (it was outside and it was going to rain). 3 days later I took it out and put it in water (rubermaid tub), I changed the water every 2 days and the ph was around 8 after a week. So the total time was about a week and a half. No clue why it was so fast:)

Here are some pics, sorry for the algea everywhere, the tank needs to be clean. I just made 2 large rocks.
[IMG]http://i129.photobucket.com/albums/p224/johno44/100_1008.jpg[/IMG]
[IMG]http://i129.photobucket.com/albums/p224/johno44/100_1007.jpg[/IMG]

Ph was tested with ph paper from my science lab at school. Its pretty accurate, but I wouldnt say exact.

I like that first rock - the one with the Buddha; Gotta love Buddha. My hubby and I have thought to maybe do an ancient greek ruin theme if we ever have the money to finish setting up the 75G.

I've been using litmus paper too. I'm lucky that our room-mate is green/blue colorblind - he sees blues and greens as shades of grey. pH 8-10 on my litmus paper are olive green shades. Between us, we have gotten pretty good at getting accuracy with them - the litmus chart is in whole numbers, but there are shade differences for the "tween" results, if you can differentiate - and having the colors translated to grey-scale makes the differences more obvious, I think...

I have no explanation for your rocks' results - nothing you did or used varies greatly from what most typically do.
Anyway, if it doesn't crash your system, Good Job!
Keep us posted :)

[QUOTE][i]<a href=showthread.php?s=&postid=10334272#post10334272 target=_blank>Originally posted</a> by Insane Reefer [/i]
[B]I like that first rock - the one with the Buddha; Gotta love Buddha. My hubby and I have thought to maybe do an ancient greek ruin theme if we ever have the money to finish setting up the 75G.

I've been using litmus paper too. I'm lucky that our room-mate is green/blue colorblind - he sees blues and greens as shades of grey. pH 8-10 on my litmus paper are olive green shades. Between us, we have gotten pretty good at getting accuracy with them - the litmus chart is in whole numbers, but there are shade differences for the "tween" results, if you can differentiate - and having the colors translated to grey-scale makes the differences more obvious, I think...

I have no explanation for your rocks' results - nothing you did or used varies greatly from what most typically do.
Anyway, if it doesn't crash your system, Good Job!
Keep us posted :) [/B][/QUOTE]

I had my fresh water tank set up with that theme, that crap gets pricey. I wish this came up 3-4 months ago I would have shipped you all my ancient ruin pieces, I threw them all away:(

That first rock was made over an inflated latex glove. If you look you can see were some of the fingers were.

"if it doesnt crash your system" are you trying to make me nervous?:p

I will keep you posted, they have been in the tank for a little over a week. So far so good

[QUOTE][i]<a href=showthread.php?s=&postid=10334553#post10334553 target=_blank>Originally posted</a> by johno4 [/i]
[B]I had my fresh water tank set up with that theme, that crap gets pricey. I wish this came up 3-4 months ago I would have shipped you all my ancient ruin pieces, I threw them all away:([/b][/quote]
That would have been cool to have had. I am planning on making silicone molds so I can cast the architectural pieces in MMLR, from pieces I can find cheap, like at garage sales, etc.

Making a mold is as simple as mixing silicone rubber with a thinner like denatured alcohol or paint thinner. Prep the piece you want a mold of (if porous, spray with poly or sealer) and then coat it with a thin layer of release and "paint" a first coat on. After that you can either paint the rest on or put it in a shallow box and pour the silicone in and place your piece into that. Once it cures, peel the mold from the original, and if you did good, you have a mold that should last at least a few castings. Use veggie spray to keep the cement from sticking to the silicone.

[b][quote]"if it doesn't crash your system" are you trying to make me nervous?:p [/B][/QUOTE]
No, that wasn't meant as a scare tactic, but I am really stumped about what happened with your rocks. Everything I think I know about cement says you shouldn't have had those results, not with the method and materials you posted. Not in that time-frame. You should really keep an eagle eye on things is all I'm saying :)

How's the "Disco Dancer" rock doing?

[QUOTE][i]<a href=showthread.php?s=&postid=10370245#post10370245 target=_blank>Originally posted</a> by Neptune777 [/i]
[B]How's the "Disco Dancer" rock doing? [/B][/QUOTE]

LOL - psychic.
I did happen to go to the LFS yesterday. It is in the main fish holding tank. A lawnmower blenny has claimed it in the name of him.
Looks good - owner asked if I could bring in a load of the Perlcrete - I told him he had to buy what I had of the Ol' Skool first - around 125lbs. [i]Then[/i] I will bring in a load of the Perlcrete. :D

So 10 day old Jiffy Perlcrete is currently in a system and seems to be fine.

no diatoms or anything? say it isn't so

You have to realize this is in a professional/retail setup, not my little 10G like I planned, lol.

No diatoms. It is getting a hazing of greenish grey algae/grunge, but most cement based rock is going to grow some algae, and I find this type the less offensive (it has no height, just a coloring, really), plus it colors the rock naturally, fairly quickly.

I wasn't planning on stopping yesterday, so didn't have the camera on me - when I take the load of rock in, I will try to remember to take it and get a picture to post.

[QUOTE][i]<a href=showthread.php?s=&postid=10370775#post10370775 target=_blank>Originally posted</a> by Insane Reefer [/i]
[B]LOL - psychic.
I did happen to go to the LFS yesterday. It is in the main fish holding tank. A lawnmower blenny has claimed it in the name of him.
Looks good - owner asked if I could bring in a load of the Perlcrete - I told him he had to buy what I had of the Ol' Skool first - around 125lbs. [i]Then[/i] I will bring in a load of the Perlcrete. :D

So 10 day old Jiffy Perlcrete is currently in a system and seems to be fine. [/B][/QUOTE]


:thumbsup: That's Excellent!

I remember you sayimg that the perlcrete rock was rather fragile/brittle after you first made it. Did it harden up well?

That first test piece, "Disco Dancing Rock" was pretty hard when I took it in - it did hardened up somewhat more than it was.
Subsequent trials are mixed just a hair wetter then I would make Ol' Skool/+ with, and these harden well.

Still not quiet as hard as just regular Ol' Skool, after the same time period, but nothing to stop one from using it if they so choose, IMO.

Newest Perlcrete
 

This is my newest test piece - I was going for something like a elkhorn, ended up with either a cross or a dragonfly, depending on your frame of mind.
[IMG]http://i186.photobucket.com/albums/x176/Insane-Reefer/dragonflyrock2.jpg[/IMG]
[IMG]http://i186.photobucket.com/albums/x176/Insane-Reefer/dragonflyrock.jpg[/IMG]

I cast this piece in limestone grit - I haven't scrubbed this rock off yet, but the sand will be visible even after that.
If you don't want to see the sand, use the sand blasting sand - it disappears.

That looks awesome!

:)
Thanks!

I decided that making rock shaped rocks wasn't the way to go. I'm going with showpieces - arches, cave systems, pillars and the like. Those are the pieces that just don't get seen in the LFS very often, as real LR, so they should sell really, really well...

IR..what is the Perlcrete recipe ? I read back a few pages and can't find it anywhere . With all the experimentation it got hard to follow for a little while. IF I can find the supplies for the perlcrete , I will be willing to be one of your lab monkey's and give it a shot.
Sorry if I just missed the recipe but I have been following this thread for a long time and I just can't find it . I am about 2 weeks away from adding water to my new 90 gallon tank so I will be needing rock soon.
BJ

[QUOTE][i]<a href=showthread.php?s=&postid=10376258#post10376258 target=_blank>Originally posted</a> by grannybj [/i]
[B]IR..what is the Perlcrete recipe ? I read back a few pages and can't find it anywhere . With all the experimentation it got hard to follow for a little while. IF I can find the supplies for the perlcrete , I will be willing to be one of your lab monkey's and give it a shot.
Sorry if I just missed the recipe but I have been following this thread for a long time and I just can't find it . I am about 2 weeks away from adding water to my new 90 gallon tank so I will be needing rock soon.
BJ [/B][/QUOTE] Perlcrete is 1/3 portland, 2/3 perlite. It has other uses besides the reef tank because it is a good insulator that does not explode like concrete with aggregate at high heat, and because it can be carved and drilled.