kmoz - judging by those pictures, it's more likely that we other folks on the forum will be looking to you for advice, rather than the other way round.

The only advice I have for you is that it's certainly possible to insert a rod or dowel through a tufa mold & withdraw it later. Several things help. For one thing, if the dowel is tapered, the taper makes it's easier to remove. Also, it's easier to remove if the dowel/rod is rolled in layers of newspaper: the dowel separates from the damp newspaper more easily than from the tufa - though some of the newspaper will stick to the tufa. Better still, after rolling the dowel in newspaper, wrap the outside of the newspaper with a layer of smooth, thin packaging tape - e.g. the Grand & Toy brand. Even that can be improved - smear the packaging tape liberally with Vaseline.

Don't try to remove the dowel until you're satisfied that the tufa's set hard and strong enough. Also, if you can, it's generally safer to remove the dowel while the casting's still in, and firmly held by, the mold - the mold helps to protect the casting from any strain exerted on it when you're removing the dowel. Finally, assuming the dowel is cylindrical or a tapered cylinder, you can usually loosen it by clamping the projecting part of it with vice grips & rotating it.

Herb

But you might want to gently twist the dowel a bit while the cement is still green.

kmoz, This is as complicated as you make it. You don't need admix to make it waterproof. I have mini bog gardens that are made from equal parts portland cement, sand and sifted peat moss that are water tight. Plain old water is fine.
You can insert and leave in place a piece of PVC tubing or a pieces of garden hose with a rod to hold it ridgid for piping your water.
A five gallon bucket will work as a mold but you may want to cut it in half lengthwise and tape together with duct tape, so it's easy to remove your piece. You should unmold in 24 hours to carve your block.

Herb, Unless kmoz is Islandgardendesign, those pictures are examples of what projects kmoz wants to do. Billie

Kmoz,

The biggest challenge with a mold such as a 5 gallon bucket will be un-molding. The wet tufa and plastic create a vacumn effect. Grease the mold well, and I suggest you use a layer of very damp sand in the bottom ofthe bucket. The sand can be brushed away upon unmolding. I'm currently trying to un-mold a pedestal base from a small mold I've used many times, but am having a hard time of it this time, grrr. The tufa is firmly stuck in he mold, which I don't want to destroy to remove the pedestal.

As for shaping, the tufa will be very green for the first 24-48 hours and you can use a wire brush or rasp, etc. to gently shape the lantern. Just be gentle as the tufa is likely to crack or break while green.

Mabel in Maine

Thanks all for the advice. I'll post some picks of the process here - I wasn't able to find much on the web about making one of these basins from tufa. As a follow up - after sufficient curing, will the block be waterproof? or does it need some sealant applied (especially since it will be subjected to constant water for 6-8 months a year)?

Herb - as Billie pointed out (I assume with a smirk), those pics are just examples of what I would like my finished product to look like.

Mabeldingeldine---Try soaking your mold in HOT water, has worked for me many times, real good on plastic molds.
Paws

Welcome to the forum kmoz. I use 5 gal. spackle buckets all the time for molds and have never had a problem getting the tufa out as they are wider at the top than at the bottom. Brush the bottom & sides with used motor oil before pouring & they'll slide out of there after 24 hours fairly easily. Keep in mind that the tufa will be quite green at this point, so if your finished casting is, for example, 6 inches from the top of the bucket, it's going to drop 6 inches when you turn that bucket upside down, subjecting it to possible breakage. De-mold it onto grass, not a blacktop driveway! Don't worry about the oil on the tufa surface - it'll disappear in a week or two.

You can immediately begin to round over the edge using the previously mentioned tools. Go slowly. You will soon enough develop a feel for it. Hose it off whenever the dust of what you've removed begins to obscure your vision.

If you need a hole completely thru, the embedded hose or pvc was a great idea. Oiling and twisting the dowel will work too. At this point, you can also put any size spade bit into a portable drill and make a hole that way. I do this all the time.

One more thing, you might want to hunt for a suitable container (smooth plastic, stainless steel, whatever) you can use to form the basin part of your fountain as opposed to hewing it out by hand. You'll save yourself alot of elbow grease & greatly reduce the chance of cracking the piece. (I'm thinking a two or three liter soda bottle filled to the top with water would probably work pretty good.) Oil the outside first. Pour your spackle bucket about half full, then press the bottle down into the wet tufa to the depth you need, keeping it centered. Now top off the bucket around the bottle to the required height. Leave the bottle in until you've rounded off the top edge (to give the center added support.) If the bottle doesn't want to come out, cut it off an inch or so above the green tufa (to give you a grip), dump the water, then collapse the sides of the bottle towards the center and that will do the trick.

After setting the mold yesterday, I removed it today and went to work. Here's some pictures of the procedure:

1. Tools used: {{gwi:71546}}

Rest assured that's not a used biohazard pail! To make the indentation I used an old bonsai pot.

2. Setup: {{gwi:71547}}

The pot was wrapped in plastic wrap, and then everything was painted with vegetable oil (didn't have used motor oil laying around).

3. Final Product: {{gwi:71548}}
The mix was 1 part portland, 1.5 parts sand and 1.5 parts peat. I made the mistake of moving the mold after pouring it, and the pot shifted to the side, but I wound up liking it just the same.

4. Profile: {{gwi:71549}}

5. Closeup: {{gwi:71550}}

Try using General Purpose 100% Silicone CLEAR to adhere the plastic to plastic then it will have a better chance of not shifting. This is what they use for the reverse letting in Pet Marker Molds and anything they want to personalize. It will be able to be pulled apart when done. I haven't tried this but they say it works.
Paws

WoW! Nice job! You did a good job rounding the edge. Very uniform. Thanks for the pictures, Now I'm going to have to try it! One more project for the list.

How are you going to handle the bamboo part of it?

Here's the finished natsume fountain in all it's (sort of) glory:

{{gwi:71551}}

Eventually, I'd like to have the basin appear to be simply resting on a bed of stones, flush with the garden, but I wasn't able to (cheaply) set that up yet. All in good time I suppose.

Kmoz that is very nice. More than nice.

You did a terrific job.
I've never seen one of these in real life. Is it circulating fountain?
Where do you get the bamboo?
I would like one of those for my garden.

kmoz-Very nice job. See it was all worth it!
Paws

Stunning piece of art there! Congrats on a PERFECT job!

I am impressed and envious! lol Well, I mean that in a NICE way. I've always wanted a water feature in my garden and this style has always appealed to me. I'm grateful that you took this on because now I can visualize it all the more.

Marly

Thanks for the compliments all. The hardest part of this project was waiting for the tufa to cure.

Tufaenough - It is indeed a recirculating pump - the water spills into a small cavity on the top, then trickles down the sides of the block. The surface texture of the tufa seems to pull the water on all sides, so the entire block stays wet.

Bamboo was purchased partially in Chinatown in Toronto, and around the corner at Walmart. Probably about $5 worth in total, with enough left over to make something else with it still.

Thanks again for all the suggestions, I'm already planning my next project.

KMOZ, what a great 1st project, you did a really nice job. I usually put a hole in my bucket or or molds, I feel it helps to demold.
bonnie