The-Artistic-Garden's Blog

A Frustrated Hypertufa Trough Maker Seeks Helpful Advice

I received an email this week asking me:

A friend and I tried one of your basic hypertufa recipes without adding the fiber mesh. Our results are very crumbly. I think we goofed by not using it, right? Where does one find fiber mesh? NewLearner

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My reply:
Hi NewLearner:

I hate to say it, but I don’t believe the lack of fiber mesh in your basic recipe was the cause for a crumbly failure. Sounds like the amount of water you used and/or wrong proportions of ingredients was your problem.

You didn’t tell me the “basic” ingredients you used, nor the ratios. Too much or too little water is often the cause of failed hypertufa recipes. Sometimes too much of one of the dry ingredients can be the culprit. Since I wasn’t there to observe you mixing up the recipe, I can’t be more specific in figuring out the cause.

I suggest you (re)read this article: Hypertufa Recipe Mixing Guidelines.

About where to find the fiber mesh – you can check with commercial concrete companies if you cannot find it in retail stores that have a good assortment of concrete products. Fiber mesh can sometimes be hard to find in certain areas of the country. I also suggest you Google “fiber mesh for concrete” and many results will come up and you’ll find online sources.

Also read the blog post I wrote on just this subject: locating silica fume and poly fibers. I believe you’ll find it quite informative and helpful.

Remember … hypertufa “success” often takes a couple failed attempts. Really. Portland cement can be temperamental to work with. Most crafters really have to get the hang of the correct water ratio in relation to the portland cement, along with following proper curing methods. Keep trying your hand at small projects (less wasted materials) until you believe “you’ve GOT IT!”

Sometimes These 2 Ingredients are Hard to Get Your Hands On

I often get asked by many hypertufa and concrete garden art enthusiasts where to find “silica fume” and “poly fibers”, also referred to as “fiber mesh”. Depending where you live, it may or may not be very easy to lay your hands on this stuff.

PLEASE NOTE! Silica fume is sometimes confused with fumed silica (also known as colloidal silica and pyrogenic silica). These materials have different derivations, technical characteristics, and applications. Silica fume is very fine like beach sand and completely black.

Silica fume and poly fibers are used as strengtheners, normally referred to as fortifying agents. They help make your cured hypertufa or concrete object stronger. Often, you’ll want to use one or the other for items such as stepping stones or very thin spheres. I do have some recipes sitting on my website that I’ll refer you to, in case you aren’t familiar with recipes and/or projects that utilize silica fume or poly fibers. Here are three of them:

Hypertufa Recipe Using Fiber Mesh (Poly fibers)  (refer to last recipe on the page)
Hypertufa Sculpture Recipe
Concrete Recipe For Very Thin-walled Spheres

How to Locate Silica Fume and/or Poly Fibers

My first suggestion is to call commercial concrete supply companies in your area. Many times they will have either fortifier, and will be willing to sell you a couple of pounds. (You don’t need much of either one in a recipe – unless I guess you’re making something collosal in size! ).

I’ve even read of people walking away with some for free, after explaining to the sales people what they will be doing with the silica fume or poly fibers. Seems the sales people get a kick hearing that Portland cement is going to be mixed with peat moss and water to make an odd concoction called hypertufa!

My next suggestion is to do what else … that’s right, find suppliers who sell via their online store. In doing a Google search today, I found EpoxyUSA.com carries poly fibers for a very reasonable price on the Fillers-Thickeners webpage. Note – I have no affiliation nor experience ordering from them. Perhaps you should contact them first to check shipping charges, etc. before you order. But I’ll wager a guess they are legitimate and probably fine to deal with.

Finding silica fume online seems to be more of a daunting task. I did find this link to the SilicaFume.org webpage. If nothing else, call them and see where you can purchase a small quantity online.

So, there you have it. I hope I’ve helped you locate two ingredients that do help make a difference in strengthening concrete and hypertufa recipes.

Be Aware Of How Portland Cement Or Mortar
In Your Recipe Will React To Various Metals

I received a question from a crafter who had read my post about using hypertufa to skim coat vertical walls. She has a metal shed that she’d like to use the technqiue on and wondered if it would work in her situation.

I told her I’d found and saved some information years ago about this very issue and would post it. So … here it is. Anyone who works with a hypertufa or concrete recipe and uses a metal mold, or has something else made from metal that will be embedded into the ‘tufa or ‘crete needs to be aware of this information.

Aluminum
Embedded aluminum roof flashing, aluminum water stops, aluminum electrical conduit, introduced aluminum powder (sometimes used to foam concrete), or embedded structural aluminum shapes may all corrode in concrete or mortar. In all cases, a reaction that forms aluminum hydroxide and hydrogen gas occurs, and may cause expansion and cracking of the concrete or mortar. The common use of calcium chloride (or other alkali compounds), and dampness of the concrete increases the reaction rate. Usually, coating the aluminum with bituminous paint, impregnated paper or felt, plastic, or an alkali-resistant coating will prevent or sharply reduce the corrosion.

Copper
Copper embedded in concrete and/or mortar is usually roof flashing. Embedded copper is practically immune to reaction with corrosive alkalis, even if exposed to constant moisture. Copper will not react with dry, hardened concrete and/or mortar. Rainwater leaching, however, may bring chlorides in contact with the metal. Corrosion may occur and result in a green discoloration or runoff. Consequently, chloride admixtures should not be used in concrete if contact with copper is expected.

Lead
Lead will always corrode when in contact with fresh concrete and/or mortar. The high pH from calcium hydroxide is the cause of the corrosion. Cured, seasoned concrete or mortar will not react with lead. Corrosion of embedded lead flashing in mortar joints will usually result in the production of a lead oxide, a white discoloration. A special case of lead corrosion, called differential aeration, occurs when a lead strip is partially embedded in concrete so that part of the strip is exposed to air. The embedded section has a different electrical potential than the section exposed to air. The result is that the strip will become polar in the presence of moisture. Gradual corrosion and disintegration of the embedded lead will then follow. In such a case, and in all other cases, the embedded portion should be coated with epoxy, varnish, asphalt, or pitch.

Zinc
Zinc is highly reactive with alkalies and will deteriorate to some degree upon contact with fresh concrete and/or mortar. The reaction is limited due to a corrosive film that forms on the outer layer of the zinc. It protects the underlying metal from further reaction. Zinc will not react with dry, seasoned concrete and/or mortar. Embedded zinc will react with moisture and calcium hydroxide to produce calcium zincate. Zinc corrosion may also occur when galvanized iron, in the form of flat or corrugated sheets and rebar, comes in contact with fresh concrete and/or mortar. Galvanized iron is coated with zinc, and will react with moisture and chlorides in the concrete and/or mortar to produce zinc chloride. The result is expansion and cracking of the concrete and/or mortar. The metal should be protected with epoxy, varnish, asphalt, or pitch.

Sculpting Hypertufa Into Realistic Rocks
For Use In Bonsai Landscapes

Jim wrote and asked:

I am an avid bonsai gardener. How do I make hypertufa into rocks with sharp edges so they will look like small mountains and fit well into my bonsai gardens? Also what recipe would you suggest for these rocks? Jim

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My reply:
Hi Jim:
Thanks for asking your questions.

First, as far as sharp edges, that is what one would call “artistic expertise”. Meaning, you’ll have to use some kind of tool (maybe a small paring knife; a screwdriver tip; or an appropriate “professional” carving implement) to scrape and carve away the ‘tufa in order to get the crevices, sharp points and such you’ll need to make in order to reproduce the look of real rocks.

Next, about a good recipe – since I know this project is for use in your bonsai garden, I don’s see why a very simple hypertufa recipe that does NOT have perlite or vermiculite in it would work. After all, these are very small rocks, and because of that perlite or vermiculte would not give them a realistic look (at least not in my opinion).

So, you could use either of the recipes found on the following page, but you wouldn’t necessarily need to use the fortifiers: Hypertufa Sculpting Recipe.

And, for something as small as what you’re making, a “final layer” would not be necessary.

Really, any ‘tufa recipe can be carved, in essence. These recipes as you’ll note don’t have the perlite/vermiculite which allows a smoother surface. (The peat moss will give you enough texture.)

OH … I would highly suggest to really sift and/or pulverize the peat moss to a very very fine texture. Again, with such small objects as you’ll be crafting, you don’t want a huge chunk of peat in your recipe!

Hope this helps get you pointed in the right direction. Good luck with all your bonsai garden projects.