DIY Rock Tutorial/Info Thread (Rocks, walls, floors, etc.)

[Electrobes]

Chapter 2

Chapter 2
Recipes and casting material

This is going to be a shorty.

Recipes:

There is an absolute stock pile of recipes out there it's enough to make any novice's head spin. The problem isn't that the high numbers of recipes are bad or anything, but it's confusing to discern which is right for you. Let's get some basics out of the way:

- In general we want about 3-5 parts of aggregate to 1 part of cement. I personally prefer 4 parts aggregate to 1 part cement... it just works for me. The trick is to remember what the cement's purpose is: glue. Cement is the glue that binds the aggregates together. Cement is NOT the body of the rock. Try not to think that you need a lot of cement to create rock.

- Your rock will take on the characteristics of your aggregates. For instance if you use just aragonite sand, the rock will act like a giant grain of sand... it will be solid with little porosity. Use just perlite? Your rock will be lighter than anything out there but will be brittle. How about dolomite gravel? Your rock will be more solid but heavier than all get out. Always keep in mind that your rock will be the very things you use to create it. Portioning the ingredients to balance out the characteristics of your rock is critical to get what you personally want.

Recipes: Here are some recipes I've used and have seen used with success:

1 Cement : 1.5 Dolomite : 1.5 Aragonite

1 Cement : 2 Dolomite : 2 Aragonite

1 Cement : 1.5 Perlite : 1.5 Aragonite

1 Cement : 2 Perlite : 2 Aragonite

1 Cement : 2 Perlite : 1.5 Aragonite

1 Cement: 1 Perlite : 1 Dolomite : 1 Aragonite

And on, and on... you get the idea. All of the above works fine… only subtle changes are noted amongst the different recipes. Your imagination is the only limit. I highly recommend you experiment with recipes and ingredients to achieve your personal favorite. Lord knows I sure have!

This picture is of my earlier work before using perlite. The ingredients at this time are dolomite, aragonite, and white cement. I essentially created a porous and solid rock, but also very heavy.

Casting Material:

- Sand: Works fine but you'll need to prepare the mold before you cast it. Dampen the sand with some water and shape out a rough draft in the sand of what you want your piece of rock to look like. You'll need a box to hold the sand in.

- Rock: If you have scrap rock lying around put it to work! This is my favorite method for making rock. I get random shapes and sizes that rock is supposed to look like. A con to this method is that you'll have to chip out the mold rock from the casted piece. The other con is that you’ll also have to invest a lot more money, time, and storage for this method. You don't need a box for this method.

- Foam and plastic: I've tried all sorts of other things. This method involves foaming, at random, a flat board then putting plastic over it. Casting is simple... just pour the mix on it. No pre-dampening of anything is needed... a slight bonus. Another bonus is that the casted piece is easily removed.

 

[Electrobes]

Chapter 3

Chapter 3
Temperature requirements, water amounts, mixing methods and requirements, and hydration

This is one of the most important posts in this rock making thread (Of course this is just my opinion!). Understanding these concepts is the key to getting great rock!


Temperature requirement: There's a temp requirement when mixing cement? Yes there is! You might have noticed that cement workers don't do cement work during the winter unless the environment is managed somehow to be warmer. While the actual chemistry is complicated to understand, the rules behind mixing concrete (Temperature-wise) is quite simple.
Rocks, while curing after the mixing of ingredients (Reacting chemically), like it warm. The warmer the rocks are during the cure, the more efficiently it hardens. On the contrary the colder the rocks are during the cure, the less efficiently it hardens.
On average, room temperature works out well for most DIYers because of the convenience of it. While not the best situation for mixing concrete, room temperature certainly isn’t the worst by far!


Water amounts: This is CRUCIAL and takes quite a bit of practice. You WILL screw up the first few times (Or many times) unless you are one lucky person. Determining water amounts when creating man-made rocks isn’t something that can be done accurately. Just because you have exact measurements in your recipe doesn't mean the same amount of water will kick the cement just right every time. It's an annoying problem... but it's just a hurdle that needs to be overcome.
The reasoning behind this is this: No matter how close you stick to the recipe amounts, the actual surface area of the ingredients always make your actual amounts vary significantly. So when the cement actually encounters the aggregates, you’ll need varying amounts of water.

What needs to be learned is adding water and realizing when enough is enough BEFORE you pour too much. It sounds odd, but cement is slower than our thought process. It first takes in the water, as you mix it, thinks about reacting with it then decides it's enough to kick it into gear. Always be suspicious of the cement... it is out to mess with your head and deceive you... always.
The biggest point to this section is to NOT pour all of your estimated water in one pour. Pour smaller amounts as you mix your concrete up until you get your intended texture. You don’t want to accidently pour more water than you need… you’ll end up with a very watery concrete that hinders the cure (chemical reaction) process.


Mixing methods and requirements: There aren't exactly many methods to mix cement, I mean all we do is just mix up a batch, but some basics should be known about. First comes using the cement mixer, and then not using one.

The cement-mixer way:
Mixing in general: Masonry methods say you should dump half of your estimated water and all of your coarse aggregate into the mixer first. Turn on the mixer then in order pour in the sand, cement, and the remaining estimated (low ball this) water.
Let it mix for three minutes. Afterward check for consistency and add water until you reach what you believe is the right consistency. Don’t be shy about taking some “test†batch out and see for yourself if it’s just right.
The non-cement-mixer way:
Dry mixing: I advocate dry mixing your ingredients before adding water. Using a 5G bucket, add your ingredients in no particular order but remember that you won't be making ALL your rocks in one mixing. I often mix what equates to about 9-10 pounds of rock per mix. This amount is good for me because I don't feel rushed when casting, giving me time to give better detail to the rocks.

Once you get your dry ingredients in the bucket, pour them out into your cement mixing bin. From there, mix the dry ingredients like crazy till you feel it sufficient. After mixing flatten out the dry mix to the floor of the cement bin... nothing tight or anything just a level field is fine.

Wet mixing: Now comes the hard part. Right off the bat you should know you will not be adding the water all at once. You will probably have to pour out some water at least 3 or 4 times to evenly distribute it and give you some warning as to the state of the wet mix. You're going to pour out some water, evenly over the mix, mix like crazy, and then repeat. There is no way to explain this without showing it live, but eventually you'll "know" when the mix is ready. It's going to feel and look like semi-dry oatmeal.

Like I said… this is going to take practice. Don't expect to get this right the first, second, or third time. If you screw up and add too much water, just add another batch mix and you'll end up with double the wet mix... but a second chance to get it right. Once you get it right you get to cast!


Hydration: Here is way more info than you probably wanted to know about hydration. In short, hydration is the reaction of water and cement. The long version:

Cement hydration
Getting ready for the “Cureâ€:
This is one of the more labor intensive parts of making rock but straight forward. After you have casted the piece in the mold, you need to wait between 12 to 18-24 hours before you take it out of the mold. This is to let the casted piece get hard enough to easily remove later on. Once the piece is removed from the mold the Cure can start!

 

[Electrobes]

Chapter 4

Chapter 4
The Cure

This is a crucial, but the most mis-followed step in the creation of our man-made rocks. I say this because this is the step where patience is most necessitated but often overlooked. The good news? It's a fairly simple step to follow... up to this point, you've already done the hard part!

What do I mean by "Cure"? Cure is a term, meaning the rocks are undergoing chemical reactions, and the one we're most concerned about is hydration, as mentioned earlier. When we say we are curing our rocks, this takes place after we have casted and removed the casted piece from the mold and are letting it “dry offâ€.

When cement workers do their thing, they follow very similar steps, in fact we use the very same things they employ... it all came from them. After cement workers cast their piece, you'll sometimes notice that there is a damp cloth covering it. Why is that?
Just because we’ve mixed our ingredients together and casted our piece, it does not mean the role of water is over… not by a long shot. I mentioned that cement should be mixed in a warm environment. The same goes for rocks curing with a little twist: They lot it warm and humid. Again the science behind this is a bit complicated, but the rules are fairly simple. Keep the rocks curing in a warm and humid environment if possible.

By adding heat and humidity you help out the hydration process, increasing the strength and in effect, shortening the Kure process (more on this later). There are any number of ways to achieve this, but the common practice is to just leave the rocks in a plastic bag, spray some water in it, close it off, and leave under the sun. In winter, you can do this by keeping the bag inside the house but by a window.

You really need to have patience and just leave the rocks in the cure process for the full 28 days. Every now and then, remember to re-spray the inside of the bag, with water, to keep the humidity up.
So in short you need to:
1) Remove the casted pieces from the mold.
2) Place the curing rocks in a plastic bag with some spritz of water in it then tie the bag off.
3) Every now and then open the bag and spritz some more water in it and tie the bag off again.
4) Repeat for a full 28 days.

That's it... tough isn't it? ; )

 

[Electrobes]

Chapter 5

Chapter 5
The Kure

If you thought the cure was easy, this step is no different. Patience and consistency is needed.

Once your rock has finished the cure process, take them out of the bag and put them in a body of water. The goal here is to leech out the pH-increasing agents that was left over from the Cure process. Our culprit? Lime from the cement.

A note about curing and hydration: A lot of people don’t realize that not all of the lime in cement reacts after mixing it with water. The process of hydration is by no means an instant one. It takes time… usually 28 days will give you about 90-98% hardness or completion. The rest of the percentage can take centuries!
The goal of the kuring process is to leech out the “residual†lime from the rocks that have not reacted during the cure process.

What type of water should we use, you may ask? Is it RO/DI water, or maybe saltwater? The good news is that it's neither! Tap water works the best, believe it or not, for kuring your man-made rocks.
The issue, unseen of course, is that all tap water is different. In my area the freakin' pH is anywhere from 8.3 and higher! The typical pH of lime (In cement) is about 13. It would make sense then that after a couple days of soaking the rocks in my tap water, the overall pH of the water reaches 11-12.
Basically one place with a lot of something will gravitate towards a place with little of that something. There’s a scientific word for this, but I am having a massive recall-fail at the moment.

I personally like having the water move when kuring. A simple pump works fine, and there really is no specific turnover to achieve. As long as the water moved somewhat, it should suffice.

As for temperature, I suggest keeping it at about room temp if possible. It seems to be the threshold to reach because it leeches the pH in the shortest time. Too cold shuts down the hydration process (It's on-going), but too hot forces even more hydroxides out than intended, causing the pH to actually increase over time as opposed to decrease.

This process can take anywhere from weeks, months, and some people even reporting a year or more! Lots of factors play into this, but your goal is about a pH of 9 or lower.

How do you test your rock for this goal of 9 or lower? Well the most common way is to take a sample from your batch. Rinse it out some before testing. Get a five gallon bucket, and fill it with old saltwater. Keeping only a heater (To avoid too big of a temp swing), and no pump... place the rock carefully and leave for about 2-3 days. After that time period, briefly mix the saltwater and then do a pH test. Anything higher than 9, I don't suggest to use in an aquarium.
If the pH tests the rock as too high, take the rock back to the kuring bin and try again another time. Keep doing this until you get the pH of 9 or lower. Should you get to that goal, the rock should be ready for aquarium use.

 

[Electrobes]

Chapter 6

Chapter 6
The Results!
Just a pre-warning, the photos just don’t do any justice to these rocks. You can barely see the actual porosity... it drives me crazy.

Texture of rock:

One of my more recent creations that is currently in my tank:

This piece I demo'ed at MACNA in the Aquarium Specialty booth:

 

[Electrobes]

Well that was fun!

 

[blaten]

Thanks electrobes! Great read and amazing rocks. Much appreciated.

 

[badger126]

So what's the most important part to consider when trying to make a very porous rock? I like how porous the rock you have made is and I'm curious as to how you get it that way.

 

[Electrobes]

Using the mix I currently use, it's pretty much self porous. It just comes out like that after casting.

 

[mgdmirage]

Such a cool writeup. I'm still really confused about once you use a rock for your mold and you chip out that rock isn't your newly created rock then hollow? Do you then fill it?

 

[luckylou]

Any chance for a video?

 

[wooddestine]

awesome post

 

[Young Frankenstein]

Thanks, the only qestion I have, if you dont use salt, how do you get the small holes ? and I agree that using salt will make the rock more weak

 

[fluffybeast]

I can guess an answer to that. Because the intent is to use only enough water for the cement to be sticky, I think it globs kind of like peanut butter, so it isn't a liquid that would fill in spaces. If you were to pile together the coarse aggregate or even the sand, there is still a lot of airspace in there, and by globbing instead of liquid filling, you'd only lose some of that porosity to the cement. Plus, perlite is naturally pore filled and those air spaces would be retained as well.


I would love to know where to get the bulk aragonite. I think fake rocks would not require the same uniform size of aragonite sand a tank substrate would and so should be a lot cheaper but still have the same buffering abilities (albeit less so in rock form).

 

[Electrobes]

Argh, I never got email notifications!

mgdmirage

Such a cool writeup. I'm still really confused about once you use a rock for your mold and you chip out that rock isn't your newly created rock then hollow? Do you then fill it?

I basically have mold rock that lie next to each other, and I pour the mix on or in between these mold rocks. After about 24 hours, the mixed (Or new rock) is still pretty "soft" and pops out of the mold rocks pretty easily.

luckylou

Any chance for a video?

I don't have a video on hand and I just moved to Fort Myers, where for now I am a full time house dad. I am having a workshop built in about a month, and am hoping to continue making on a smaller scale to experiment and keep my skills for my return to the industry after my son goes to school full time (In a couple years).

wooddestine

awesome post

Thanks!

Young Frankenstein

Thanks, the only qestion I have, if you dont use salt, how do you get the small holes ? and I agree that using salt will make the rock more weak

I get a crazy high porosity from the mixture I compose, using perlite (for instance) helps create the nooks and crannies, along with the aragonite. The same would go for dolomite, but it is heavier.

fluffybeast

I can guess an answer to that. Because the intent is to use only enough water for the cement to be sticky, I think it globs kind of like peanut butter, so it isn't a liquid that would fill in spaces. If you were to pile together the coarse aggregate or even the sand, there is still a lot of airspace in there, and by globbing instead of liquid filling, you'd only lose some of that porosity to the cement. Plus, perlite is naturally pore filled and those air spaces would be retained as well.


I would love to know where to get the bulk aragonite. I think fake rocks would not require the same uniform size of aragonite sand a tank substrate would and so should be a lot cheaper but still have the same buffering abilities (albeit less so in rock form).

fluffybeat, pm me if you are still looking for a supplier. I can give you some info about that.


I am hoping to get back into the posting and experimenting swing of things soon. I love making rock and staying current (Or breaking the mold, niuk niuk niuk) in rockscaping!​

 

[JasonBJones]

I thought I would share a tank I did where I made all the rock out of a similar mixture.

This was my last tank, a 20g AIO. Here is the start:

The recipe I used was 1:2:2 of cement:sandyster shell. This picture shows the tank after about 7 or 8 months. The rock had started encrusting with coralline pretty well by this point and was indistinguishable from regular live rock.

I was very happy with the rock and will use this mixture for any tank I do with a wall. I much prefer using this over foam.

 

[that novice guy]

I thought I would share a tank I did where I made all the rock out of a similar mixture.

This was my last tank, a 20g AIO. Here is the start:

The recipe I used was 1:2:2 of cement:sandyster shell. This picture shows the tank after about 7 or 8 months. The rock had started encrusting with coralline pretty well by this point and was indistinguishable from regular live rock.

I was very happy with the rock and will use this mixture for any tank I do with a wall. I much prefer using this over foam.

wow that looks so cool!!!

 

[Electrobes]

Nice job, I like the texture you have in there!

 

[MarvinsReef]

wow that looks so cool!!!

+1. Turned out really nice.


Sent from my iPhone using Tapatalk

 

[Davesgt]

That is freaking awesome!! id love to do a back scape like that