Introduction: Make a Japanese Garden Lantern Out of Hypertufa

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Japanese garden lanterns are beautiful. Traditionally made from cut stone, they are also very heavy, and frequently rather expensive. This Instructable will show you how to make a similar lantern of your own for as little as $15 in materials (2016 prices), though the final cost might be more than this depending on what materials you might have on hand and what you can easily get access to. Also note that "$15 in materials" doesn't mean "getting the materials will cost around $15"— it means, for example, that the small portion of cement you use will only cost a dollar or two, but buying a whole bag of cement (and it is only sold in large bags) will cost considerably more. This is also true of the other necessary materials. To obtain the basic units of these materials as they are commonly available for purchase might run $30 or $40 (again, 2016 prices). You could use the leftovers to make multiple lanterns! Or use the mix for other outdoor projects like planters or fountains, both of which are very suitable for making out of hypertufa. The final product here, however, will be a completed Japanese lantern that is about twenty inches tall and has a light fixture inside of it for mounting an electric light bulb.

Briefly: what is "hypertufa"? Hypertufa is a mixture of Portalnd cement, sand, pebbles, vermiculite, and plant matter (and sometimes one or two other ingredients) which, once it sets, is very durable, lightweight, and resembles "tufa" stone such as has been used for hundreds of years in England as water troughs for horses. Except that hyper-tufa is "better" (really, just different) from "tufa" in that it can be easily created by a single individual, requires no stone carving skills, and produces objects that are a fraction of the weight of their stone equivalent. Pretty neat when you think about it. And it makes rather nice Japanese lanterns.

Once the materials are assembled and the forms have been created, it should take the average person about an hour to mix and cast the hypertufa into its molds, and then about a week for the mixture to cure (longer cure times will make for a stronger structure-- the industry standard is 28 days). Creating the molds can take as little as an hour or two if you have the necessary materials and tools on hand and have a well-organized sense of what you want to accomplish and how to make it happen. This Instructable should help with that.

The pictures show two lanterns I made from hypertufa. Both were originally wired for electricity. The taller one is hollow all the way down. Both have "light boxes" and removable tops.

Supplies

To make the hypertufa mix:

  • Play sand, 2 qts.
  • Portland cement, 1 qt. (you do not want "concrete", or "mason mix", or "mortar mix", or "pronto mix", or "stucco"-- you want plain, simple, basic Type I Portland cement)
  • Although I originally recommended 1 qt.of peat moss as plant material, today I recommend a an equal amount of coir. Coir is coconut husks which have been shredded for use as ground cover. It makes excellent hypertufa mix, though it is somewhat chunkier than peat moss. More importantly, coir is a renewable resource-- peat moss largely is not. Note that many commercially available peat moss is often sold with Miracle Gro® or some such fertilizer added-- this fertilizer will compromise and weaken hypertufa and is undesirable. If you decide to use peat moss, you should acquire peat moss without added fertilizer. If you accidentally get some peat moss with fertilizer, you can also rinse it well before using it to wash away most of the fertilizer, though you cannot mix it with the other dry ingredients until it itself is dry again and since peat moss is built to retain moisture, this can take some time.
  • Perlite, 2 qts. (or substitute same amount of vermiculite-- in either case again make sure it does NOT include added fertilizer like Miracle Gro®, which is a common additive).
  • If you live in a climate that has winter freezing temperatures, you will also need about 1 sq. foot of shredded fiberglass sheet fabric
  • Tap water, 2-3 cups
  • Two large plastic mixing tubs (one for mixing the hypertufa, the other for dumping the dry ingredients into and back out of as you prepare it)
  • Strong rubber gloves (I like to use "Bluettes"), and a filter mask a good idea too (the powdered cement is a fine dust that you really don't want coating your lungs, trust me on that)
  • For clean-up of the cement mix which will adhere to everything it touches, I have read about though not yet tried a product called Mean Klean which is a concrete and mortar disolver composed mostly of eco-friendly and surprisingly effective yet non-toxic glycolic acid. It is inexpensive and readily available. Also, if you are confident with it, you can use a very dilute solution of muriatic acid on any hypertufa mix spills as long as you have baking soda on hand to neutralize it with immediately afterwards. *Space. You need a suitable outdoor area in which to mix your ingredients and pack your molds. A driveway or garage might work fine, or a backyard or even just a patio. But it needs to be a space in which you can make a mess. You probably should not try to create a hypertufa lantern in your bathroom or kitchen, and if you try you will probably regret it.

    To make the casting forms:
  • Scrap wood pieces of various sizes & thicknesses; I used some discarded painting frames made of easily-sawed pine and some pressboard from a discarded shelving unit.
  • Glue (wood glue will work for most purposes but a strong contact cement will also do. What I had on hand was a product called E-6000 by Eclectic Products, Inc. (available from Michael's) which they advertise as “industrial strength adhesive.” I don’t know if I would go that far, but it's pretty strong.)
  • Kitchen plastic wrap, one roll; alternatively, you may use a sheet of "painter's plastic". Husky's Painter's Plastic (available from HomeDepot and viewable HERE) is wonderfully thin and though it punctures rather easily, it works very well for preserving water in hypertufa mix (though a 400-foot roll is much more than you will need for this project)
  • Large plastic garbage bags, pref. puncture-resistant or heavy-duty, 3-4
  • Various forms (bucket, plastic planter, lampshade, serving dishes, etc)
  • Optional: -Beveled glass tiles

    To light the lantern:
  • Ceramic light fixture (a Craftmade K212-O Porcelain One Piece Keyless Lamp Holder works well and costs under $2. Use a fixture without any switches or pull-chains, make certain that it is ceramic and not plastic
  • Light bulb, pref. a compact fluorescent or LED which won't produce much heat (not that heat will bother hypertufa once it has set completely)
  • Copper wiring, 10'-20', and associated plug
  • To make a paper liner for the windows of the lantern, which is entirely optional: sheets of rice paper, a Sharpie marker, some clear polyurethane-- see Step 4 for more details on this

Step 1: Before We Begin: Lantern Theory

Before we go much further it will be useful to review the theory of the construction of Japanese lanterns and explain exactly what hypertufa is.

THE LANTERN:
A Japanese lantern or “to-ro” has a distinct style, and is composed of several distinct parts. The one you make may deviate from the style demonstrated here, and still be very Japanese in its format. A standard Japanese lantern like the one demonstrated here consists of the following elements, from top to bottom:

A&B..) Ho-ju or ho-shu ( lit. “jewel”) - The onion-shaped finial at the very top.
C.) Kasa (lit. “umbrella”) - A conical or pyramidal umbrella covering the fire box.
D.) Hibukuro (lit. “fire sack”) - The firebox.
E.) Chu-dai (lit. “central platform”) - The part on which the fire box rests.
F.) Sao (lit. “post”) - The supporting main post, often missing or replaced by legs.

There are various Buddhist meanings attributed to these items as well, but I will not review them here.

You need not follow my own design exactly, but if you want your own lantern to look like a Japanese one, here are some guidelines for constructing your forms:

The umbrella must be wider than the light box and its platform, and is often wider than the base as well. Lamps with very broad umbrellas are very attractive. The umbrella is often divided into panels like the light box, and often the number of panels matches and lines up.

The firebox must be narrower than the platform below it, and taller than it. It must also contain at least one and as many as six perforations/ windows. The firebox may also be made cylindrical. The most frequent arrangement of windows is six windows on six panels of a six-sided box, though a six sided box could also have only three windows that alternate with solid panels.

The platform must always be wider than the box itself and wider than the top of the base it rests on, though not wider than the umbrella, and must not be taller than the box (usually it is less than 1/4 the height of the box). Also, the basic shape of the platform frequently mirrors that of the box: if the box is square, the platform is also often square; a round box typically has a round platform; a hexagonal box, a hexagonal platform (this is not a hard and fast rule, and I do not follow it myself here). Note that the platform, however it is constructed, is usually made so that it's bottom side slants upward and outward from the top of the base.

The base: the base may be nothing more complicated than a pillar, although if a pillar, the pillar itself typically flares out at the bottom so as to keep it from easily tipping over. The pillar may be very short, even less than the overall height of the box and umbrella (for example, a lantern for a table-top) but the flaring rule still applies: if a pillar, the bottom is wider than its top. Pillars may also flare at their tops, but this is optional. Bases with legs will have between three and four legs, three being by far the most common if not the most stable (getting all four legs of a 4-leg lantern base to be the exact same length and therefore not wobble can be very difficult and the added stability is not always worth the effort, whereas a 3-legged base will never wobble).

WHAT IS HYPERTUFA?
Hypertufa is a a mixture of Portland cement and other materials which combine to produce a stone-like substance of exceptional durability while also weighing much less than standard poured cement and costing much less than stone to manufacture. It is often used to make garden planters– its use here is a variation on that theme, using hypertufa to make a garden object designed to house a light rather than make a planter to house a plant. Hypertufa tends to sag somewhat while it cures unless it is supported on all sides, so the use of molds is necessary. Properly mixed hypertufa, however, does a reasonably good job of holding its own shape as long as the scale is relatively small, though I would never build anything larger than a teacup with hypertufa without some kind of form on either the inside or the outside. Creating these forms is the first challenge of making a hypertufa Japanese garden lantern.

Step 2: Making Your Molds/ Forms

In order to create much of anything in hypertufa, you will need to use molds. As previously mentioned, the hypertufa mixture, though stiff (if made correctly) will tend to sag as it cures and needs to be held securely in place by a form. Note that anything and everything that the mixture attaches to while curing will become more or less permanently bonded to it– glass, metal, and most plastics. This is great in some senses (if, for example, you wanted to embed objects into your cast pieces), but can be problematic in others. It is very important when finished making a batch of hypertufa that you wash down every surface of everything it has touched. Clean-up can never be left “for later,” because “for later” easily means that it will be too late.

Also be prepared to be very patient. Although I could do it much faster now, the process of making this lantern took me almost a week to plan, and more than three days to finally execute, and then I had to wait the additional cure-time of at least another week. This Instructable means that you won't have to spend quite that much time doing the prep work, but you cannot rush the process of curing the hypertufa-- If you remove any of the pieces from the molds too soon or allow them to dry out before the week is up, the mix will not have set enough and your pieces may break! You have been warned.

MAKING YOUR MOLDS (in no particular order)

The Umbrella:
For this particular hypertufa project, I used a discarded lampshade from a halogen floor lamp as the form for my umbrella– it was broad as well as very shallow, which gave it the proper shape. Indeed, it was the inspiration for the whole lantern, in my own case, and was very easy and happened to be readily available.

The Platform:
For the platform, I used a large serving dish. It was important that this piece be smaller in diameter than the umbrella, that it be flat on the bottom, and that it be wide enough across the bottom to accommodate the ceramic light fixture plus an inch or two. I wrapped the dish in plastic wrap, placed the ceramic fixture in the center, and then covered it and the dish with another layer of plastic wrap– once filled with hypertufa, this will look somewhat like a large flattened donut.

The Legs:
For the legs, I used a cheap bucket from the 99 cent store for the outside and a plastic garden planter to provide structural support for the inside. It was important that these two shapes more or less match in their slopes, that the space between each of them be about an inch to two inches on all sides (too thin and they won’t hold up the lantern; too thick and they become ungainly). To create the arches between the legs I used some foam core that had come with the delivery of my computer: it was flexible yet stiff, and just the right thickness for this project. I cut three pieces the exact same shape and wrapped each in plastic wrap secured with masking tape. I also included, at the bottom of the bucket, a small wooden “peg” to allow the future electrical cord to travel through (see illustration).


The Lantern:
The design and execution of the lantern was the most time-consuming and difficult of any of the pieces I made. For the lantern itself, I decided on a six-paneled design because that was most familiar to me and seemed relatively simple. I also had several pieces of beveled glass that I wanted to use to make the window shapes (note:I did not intend to “mount” these glass pieces IN my lantern– I only used them to create a set of shapes, though I suppose they COULD have been mounted in the design if that had been my intent).

The important thing was to create six uniform panels, each about an inch thick, with sides that sloped very close to 60 degrees, that were all the same height, and were flat on the top and the bottom. Exactly how YOU decide to go about this will be up to you. I did it by cutting 12 wooden trapezoids pieces out of some scrap lumber. These had 3" wide bases (their thickness did not matter much). I then mounted these on a board in two carefully aligned rows that were spaced exactly 4" apart, giving me the basic form to create six panels that were 3" wide and 4" tall. It was important to create panels that were at least this high so that I could eventually insert a light bulb into my lantern; if I had gone much shorter, I would have had far fewer light bulb options to work with.

To create the openings for the windows I made six uniform stacks of my beveled glass pieces between blocks of wood (all connected by masking tape), and glued these stacks onto the board between the trapezoid end pieces (see my illustration of this board). It was important that these stacks be at the same height and, for my purposes, that they be closer to one end (i.e., the top) than the other. It was also important that the stacks be tall enough to go “all the way through” the form so that they would create actual windows.

Incidentally, a standard light switch cover is 3" wide and just over 4.5" high. They would have made excellent guides for my forms if I had thought to use them, and would have produced panels only half an inch taller, which would probably have looked just fine. Live and learn.

Note: you may be tempted to design a mold that will allow you to cast the entire fire box as single piece with openings for the windows and a hollow space in the center for the light bulb. Let me forewarn you: I have tried this several times, and so far every attempt has ended in disaster: it is very difficult to extract the cured fire box from such a mold, even if the mold is only a temporary one designed to be discarded once you are finished. The delicate frames around the window openings are both very difficult to properly pack with hypertufa mix-- even thin mix-- and very likely to crack and come apart in the end even if you allow the cement to cure a very long time before extraction. Once cracked, re-attaching broken fragments of hypertufa is not easy! You can try moistening the two sides of the broken pieces, sprinkling them with pure cement dust (while wearing gloves), and then carefully bracing them together until the cement cures, but I have had only moderate success with such bonds.

The Jewel:
This is a very small and simple element. I took a rounded dessert dish from the kitchen and lined it with plastic wrap. It guaranteed me a final round shape that was the correct aesthetic width, but any number of other mold shapes would have worked as long as they were small enough and curved up evenly around the sides.

Finalizing the Molds:
Once all of these molds were created/ acquired, they all had to be completely lined in plastic wrap– it took several lengths of it to completely line the form I had made for the panels, and at least two or three to line the bucket and garden planter. Remember, the hypertufa mix will adhere to any surface it is allowed to cure against– the plastic wrap is the only barrier between your molds and the mix. The more of it you use, the more protection it will offer, though the less detail you may achieve in your final pieces.

Step 3: Casting the Hypertufa

Dry Ingredients:
Once all of the molds were covered in plastic wrap, I prepared the hypertufa mix.  I mixed all of my dry ingredients in a plastic tub, being careful not to breathe in any of the extremely fine powdered cement– Portland cement becomes airborne very easily, and you cannot scoop it into anything without creating a cloud of dust around you.  This dust contains lime, and is a throat and lung irritant which should be treated with respect and avoided when possible: only mix where you will have adequate ventilation and can clean up easily.  Also, avoid getting  cement on your skin– its high alkalinity can cause a chemical burn that can make your skin peel.  Always wear protective gloves when using cement for any purpose.  As much hypertufa as I have made in the past few years, I have never touched any of it with my bare hands until it had cured.

A bit about the other ingredients: the presence of perlite is what will make your final pieces light.  The perlite does not retain or absorb water, just air-- if you want to, you can make your mix of nothing but cement and perlite and it will be quite strong and amazingly light.  You may substitute vermiculite for the perlite, though vermiculite will retain water and your final pieces will not be as light as with perlite.  The peat moss will imbue your pieces with a rugged rock-like quality and will make them suitable for colonization by moss (note that peat moss is often considered a non-renewable resource, and you may use any number of other plant refuse materials in its place-- grass clippings, hedge trimmings, bark, fine wood chips, etc., even shredded paper).  The sand will give your final pieces a pleasant texture and solid strength. I never leave it out.  If you live in a climate that freezes seasonally, you will also want to add additional materials to keep your lantern from crumbling apart over time: fiberglass sheet cut into strips or squares and added to your mix will have the effect of preventing it from cracking.  It is readily available over the Internet, and is frequently carried locally by outdoor and camping supply places that sell canoes and kayaks (fiberglass is used to repair hulls).

It is important to mix the dry ingredients thoroughly before adding any water.  I find that completely emptying these ingredients into a second container and then back again into the first is the only way to ensure that they become completely mixed.  If you do not mix them completely, the cement will cure unevenly and your final project will be unstable.  Also: any mixing container will have corners, and these corners are where dry materials will tend to deposit themselves unmixed-- scrape them out regularly with your gloved hands as you mix to prevent this.


Add Water:
Once the dry ingredients are mixed, it is time to add water.  This is where hypertufa becomes more art than science.  How much water?  “Enough” water.  You need to add only enough water to allow the mixture to become something akin to cookie dough in texture.  If it is so thin that it won’t  hold its shape in your molds, you will need to add more cement powder (it is the cement powder that sucks up the water).  If it is so thick that you are getting clumps, you will need to add more water.  Only add water in very small amounts!  It is easy to add more cement to your mix, but impossible to take any water out of it!  And it takes surprisingly little water to activate any given batch of hypertufa.  There is no need to rush this process– the cement will not begin to cure for several hours, so take your time to do it correctly.  If you add a lot of water in the beginning, your mix will  end up soupy...  And it will weigh a ton.  Also note that though it may seem counterintuitive, wetter mixes are ultimately not as strong as more crumbly ones.  Your final mix should stick to your gloves just like cookie dough would stick to your hands, maybe a little stickier/ wetter.  It is then time to start packing it into your molds.  (There are many web resources on the nature of hypertufa and on the theory of cement curing– they are worth reviewing.  Cement.org has a very good article here: http://www.cement.org/basics/concretebasics_faqs.asp)

Step 4: Final Act: Clean-up, Trimming, Electrical, and Shades

After Casting:
The most important thing to do once you are done casting the hypertufa is clean it all up and rinse off everything it has touched– floors, gloves, tools, etc.  Also, avoid rinsing leftover mix down your drains, as cement will also cure underwater and enough of it can create a solid plug in your plumbing that no amount of Drain-O will ever be able to remove.  This is the time to break out the "Mean Klean" product mentioned in the first step: spray it on all surfaces the cement mix has touched and apparently it will ensure that none of it sets.  If you have extra mix when you are done, consider making a small planter out of it– make sure it has a hole in the bottom for drainage, and that it will stand up when it has cured (either give it legs or make sure it has a flat bottom).

You must now wrap up all of your pieces in plastic bags to help conserve moisture as the hypertufa cures, and you should revisit your pieces regularly over the next week or more and spritz them with water to keep this process moving along.  After 24 hours the mix should have hardened enough for you to pop all of your pieces out of their molds (gently, gently– the cement is still very delicate and will break easily!) and have a look at them.  If you make your panel pieces the way I did-- in a row of touching forms-- You should be able to break apart any of them which were still touching when the cement was cast.  This is also your best opportunity to even out any rough spots on any of your pieces using hand tools or abrasives. 

If you are working outside and have a flat driveway, you can begin by taking the umbrella piece out of its mold:  place it face-down and move it gently in grinding circles on this rough surface to produce a very smooth and perfectly even plane on what will be the underside of your umbrella (make sure you wash down whatever mess is left behind: all of this cement is still curing, and will cure into a permanent white spot on your driveway if allowed to dry there).  This leveling will become important to prevent light from leaking out between the umbrella and the firebox once the lantern is assembled and lit.  Likewise, you can "roller-grind" down your platform and the edges of the panel pieces (leave the legs be– they are still delicate and should not be messed with yet).

I took this opportunity to also grind my “jewel” down into a more onion-domed shape using a Dremel tool.  The cement was not quite so hard that this wasn’t possible, but it still took me at least 20 minutes to grind off enough cement to give the jewel its characteristic point (see photo).

Now that everything is smooth, you can mix up a very small batch of mortar mix– just cement and sand, in a combination that is almost soupy but still slightly stiff, using all the regular precautions– and use it to bind all of the panels of the firebox to your platform and to each other.  Covering your work surface with plastic sheeting, begin by placing a dolop of the cement “glue” on the bottom of each panel and one side, place that panel on the platform about where you think it should go, then do the same to the next piece and put it in place next to the first, and so on until you have completed a ring of six and have made a hexagon.  Wipe up any drippings as best you can with a damp sponge, cover the assembled pieces with plastic again, and let sit for another 24 hours.  Then you can uncover it again and do your best to even up the top edge of the hexagon so that it will fit smoothly against the umbrella.  You can do this by mixing up yet another small batch of mortar, putting it only on the top edge of the firebox, and then placing something you know to be flat on top of it (I used a sheet of glass wrapped in plastic wrap) for at least 24 hours.  Once this mortar hardens, you will be guaranteed a perfect fit between firebox and umbrella.

Final assembly of the lantern is straightforward: once all of the pieces have cured under plastic and have been kept moist for at least a week, you may uncover them and complete the assembly.  No more mortar or cement is necessary: the jewel for the very top only needs to rest on the umbrella which only rests on the firebox which is already attached to the platform which only rests on the legs. 

Electrical:
Between the platform and the legs is where you can place the ceramic light fixture, and run its electrical cord down the hole in the center of the tripod piece that was created by the wooden block discussed much earlier, and then to your power source.  As always, make sure this electrical connection is well protected against possible moisture– sealing it with silicone is not a bad idea.  If you do not have any experience working with electricity, please proceed with caution:  unexpected electricity is frightening at best and dangerous at worst!  Trim the ends off of your copper two-ply cord and secure each of the two strands of one end of the cord to the two electrical connecting screws on the ceramic fixture.  Tighten these screws well, and cover them with a layer of electrical tape (none of this work will be visible-- err on the side of caution).  At the other end is where your plug should be.  I leave the plug part up to you.

Shades:
Many original Japanese lanterns had paper liners to diffuse the light inside them, and you can certainly use such a device in your lantern if the wattage of your bulb is not too bright (anything incandescent over 40 watts will run too hot-- any compact fluorescent bulb will probably be fine).  If you decide to include a lampshade like this, out of paper, it is important that the paper be able to withstand the heat of the bulb in your lantern, that it be suitable for exposure to the outdoors, and that it be thin enough to allow most of the lantern's light to flow through it.  Ordinary printer paper, for example, will probably be too thick and your lantern will look dark.  I took a sheet of very-thin rice paper, decorated it with a metallic permanent Sharpie pen in swirls, and then painted each side of it with Zar "Ultra-Max" interior waterborne oil-modified clear satin polyurethane.  Once the polyurethane was dry (a couple of hours) I simply slid the paper in between the light bulb and the interior walls of my lantern, put the umbrella and jewel on top, and I was done.