Continued From Above...
New Tip! If you place your rock in tank with low light for two weeks to a month, you can avoid most of the bright green covering algae – low lights allow the rock to settle in without being attacked by algae so badly, or so it seems, IME…
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And in conclusion, I'd like to address
"Expectations". I have a feeling that some people are expecting the rocks they make to be as hard as cement blocks or cement stepping stone, because, after all, they are made with cement, so it should be, right? Well, in this case, no - they won't be.
Let's compare our “mud” to a typical cement pour “slurry”.
First, poured slurry's are made with a higher ratio of cement then we usually use. Next, they add enough water that they can pour the slurry - much like an ice cream slurry. I've never been able to pour my mud; we try to make ours as dry as we can and still have it stick together. Now take a look at the aggregates - they use dense sands and gravel, we usually use calcium based substances when we can - there is a marked difference in each of these as far as strength goes.
And finally, when cement is poured, they try to get it settled down - they drag tools over it to smooth it and make sure it is even and all that. We go for as much openness as possible, and we try not to pack the mud if we can help it.
Looking at it like this might help people come to a better understanding of what a reasonable expectation of their rock might be.
Our rock is going to flake and shed. The more porous the rock is, the more likely it will be to do so. The better the mud is made though, the less you will see of it. Maybe you have seen a box of real live rock just after shipping. If you have, you probably noticed the rubble in the bottom. Most distributors are not in the habit of making up the extra weight in a box with rubble - that would be bad business. Most of that rubble simply came from the rock during shipping. Calcium based rock is not the strongest in the world, and essentially, our rock is calcium based.
But flaking and shedding are not the same as brittle rock. Your rock is brittle if you can snap large pieces off after a month or two. Small bits rubbing off is not necessarily indicative of failed rock, those could just be pieces that didn't get adhered well.
My first piece of advice would be to wait. It takes a month for the curing process to reach near completion and the rock to reach something close to its final strength. If your rock seems brittle or flaky, beyond what you should reasonably expect, just leave it alone for a month, in a moist (not wet), warm environment, like a plastic bag. Some of the early salt rock I made
seemed really brittle, too brittle to use, certainly, for the first couple of weeks. It was when I later found it again, in the bottom of a bucket outside, that I realized how nicely it had hardened up. If after leaving it alone, you can easily snap sizable portions off (golf ball sized?), then you have a problem.
My next pieces of advice would be to use a stiff bristled brush, like what you use to clean your grill, to give your rock a good once over when it reaches about four weeks old (or after the pH test in Jiffy Rock). This will remove about 90% of the shedding and flaking, if your shedding and flaking isn't due to rock failure that is. If you have done this and a couple of weeks later it is readily shedding, then I'd say you might have a problem.
Remember that even slight variations can make a huge difference. Humidity and Temperature at casting and during the cure can make drastic differences. A tablespoon of water can make a difference on smaller batches - too wet and too dry can be a fine line. Differences in the cement itself can wildly vary - every plant uses its own recipe to make the clinker. Differences in local materials used for the recipe can ofter vary with availability and cost. My white cement is going to be different then Neptunes' cement, and his, even from the same plant as Sunkools' may vary as well, from lot to lot.
Salt can mess up the strength of your rock, so if you used salt, think about that. If you added it upfront, with the aggregates, you may have over-mixed it and too much salt mixed into the batch. Try adding the salt after the mud is mixed and ready - and just lightly mix it in.
A ratio of 1:3 to 1:5 is best for us. 1 part cement to 3-5 parts "other", which includes salt.
If you are trying Jiffy Rocks, do not remove the salt prior to baking.
And finally, realize that even the best made rock can still chip and shed once in a while. Moving it around in your tank, bumping it against each other (esp larger pieces), will inevitably cause bits to shed or chip off, unless you went for rounded ball like shapes, which seem to loose less, but also seem less porous and less attractive too.
I hope this helps a few people out there. I know that having something you worked hard on, that doesn't turn out like you wanted, can be disappointing. Hopefully this will help people understand what they should expect, and what they can do to correct it...
Well, I think that about covers my repertoire. I apologize for the length of this post, but hopefully some of you will find something of use…
I encourage the rest of you to take some time to write up your experiences and tips and share them with us – by sharing our experiences, we all learn and get better and better at making our own rock.
Good Luck, and Rock On!
