Curing Hypertufa For Success

Don’t Rush This Step or You’ll End Up With a Disaster On Your Hands!


Many a hypertufa maker has had the sad experience of having their project start to crack, crumble or not even set solid. It just starts falling to pieces soon after it starts to cure. And many remain baffled as to why it happened.


They followed the recipe to a “T”, but after they applied the mixture to the mold, everything seemed to start going downhill from there. Although it’s said that making hypertufa is almost as easy as making a “mud-pie”, there are some important facts to know that will greatly increase the odds that all your ‘tufa projects will be successful.

Even a few minutes without the right level of moisture can cause severe cracking and the loss of many hours of work.


Unfortunately, even a slight breeze in your workspace can rob enough moisture from your mixture to cause it to fail. The less air movement around you, the more moisture you’ll keep in. Avoid breezes while you are working. Sorry, you definitely don’t want to have a fan pointed at yourself to stay cool while you’re working on your project!


If you are doing your hypertufa project outside, dealing with breezes can be frustrating. Mother Nature isn’t very accommodating in letting us know when a breeze or gust of wind will happen. Try to find a sheltered spot you can work in.


Covering & Protecting Your Wet Form


The Mixture is Applied and Your Object is Ready … Now What?


You’ve applied all the hypertufa mixture and are happy with your garden art object so far. Great … you’re moving along in the right direction.

Here’s your next step: carefully place your object into a large black plastic trash bag (or similar) and seal it up tightly. (If your object is too heavy to lift, then do your best to cover with black plastic. Keep in mind you are trying to retain moisture to help the object dry slowly.) Plastic trash bags, plastic roll sheeting, anything that is air and moisture tight will also do the job.


Additional step: many ‘tufa makers will thoroughly mist the object with water before sealing up the bag. As I’ve said elsewhere on these pages, there is no exact science to anything regarding hypertufa. That includes the “best way” to cure it. It’s frustrating, but the truth is while one technique may work for one ‘tufa maker, that same technique may not be successful for another. Trial and error will show you what works for you.


Seal the bag as air tight as possible. You may want to inflate it a little to help keep it from touching (and possibly making an unwanted impression on) your object’s surface.


We’re moving right along … what’s the next steps?


Sun or Shade For the Best Cure?


Two Options That Will Work In All Types of Climates


Two Options: Place It in Direct Sunlight or Keep It In The Shade … Either Will Work


Here we go again … one hypertufa maker swears by one method, and another says “I’ve never had to do that. My pieces always come out great”. OK, take your pick. Try it either way. From my experience, these both work, and depending upon how large an object you’ve made, the spot you are able to leave it undisturbed during the curing process and other factors like these, will determine which method you will use or have to use. It’s up to you.

If you cannot place your project where it will receive direct sunlight, fine. Your next step will be to periodically open the bag, mist the surface to keep it moist, and reclose (or recover your larger object) after misting.


If you can place it where it will receive direct sunlight, that’s fine, too. Try to put it where it will get as much direct sun as possible. Because the bag is sealed, it creates a very hot environment. The heat will cause a lot of moisture to be released from the hydrating cement. The moisture will condense on the inside of the sealed black plastic bag and now you have an “automatic” water supply that will help keep your object properly hydrated while curing. A built in “mister”.

This First Stage of Curing Lasts About 2 to 4 Days


How long does it take a hypertufa project to dry? It depends upon the humidity and temperature. And … the recipe you used; also how thickly you applied the ‘tufa to the mold. This is why making hypertufa is not a set of cut and dry rules. Experience in experimenting with recipes and different types of projects brings you the expertise, just like everything else in life!


After approximately 24 hours you will want to test your new, and still curing, hypertufa object. Carefully open the bag (or uncover) and see if your fingernail can scratch off any ‘tufa. If you can, seal it back up and wait another 12-36 hours. When you can’t really scratch any off (without some difficulty), you’re ready to unmold your object. Your object is still a bit fragile! Remove from the mold carefully.


If you want to add texture to the object’s surface, you need to do that now before you move on to the next step.


Caution: when handling damp pieces you should wear your gloves! Your hands need to be protected. 

Please refer to this MUST READ article: Hypertufa Safety Guidelines.

The Final Steps of Curing


You Can’t Rush The Cure So Relax! Give Your Project The Rest It Needs 


Gingerly place your object back into the plastic bag and seal tightly. You can now keep your object at room temperature. Continue to keep it moist, misting occasionally if needed. Allow it to cure for at least another week but the longer it can slowly cure in a moist environment, the better.


At this point, most ‘tufa makers will keep the object bagged up for a month or more. (I’ve seen it written that a one month cure time can result in 25% stronger ‘tufa). As my dear Grandma used to say, “Patience is a virtue”. You too need to be patient. Remember what I just told you. The longer and more slowly it can cure in a moist environment, the stronger your hypertufa will be. Curing will also take longer at cooler temperatures.


Alright, now you’re ready to get rid of that black plastic bag! Your new garden art object can be removed and left until it is completely dried … you’ll know if it sounds hollow when tapped.


You’re not quite done yet. There is one more important thing to consider …

Cured Hypertufa is Very Alkaline


Due to the Portland cement, the ‘tufa ends up being very alkaline. If you have ever seen a white powdery residue on new cement, that is the free lime leaching out. This lime causes the alkalinity. Most agree that the lime is toxic to most plants and therefore needs to be leached from the object if you are going to use it as a planter.


Here’s where “I have success doing it this way” and “I have success doing it that way” comes into play again. You can find many varying methods on leaching out the lime. Personally, I have successfully followed an easy method: I soak my ‘tufa planter in a larger container of fresh water. I change the water every day for 3 days. It is plant safe by then.


Note: The lime can still burn your skin so wear your gloves. If the planter is too large to fit into another container, I’ll hose it down once or twice a day for 3-5 days.


Other recommendations are to leave the planter outside for 1 or up to 2 months, allowing it to weather naturally by being rained upon. I’ve even read of leaching baths concocted from various chemicals — and chemicals that are not very user friendly. I’ve read of others spraying down the hypertufa with household vinegar. From my research and experience, I wouldn’t consider the chemical or vinegar suggestions as satisfactory methods.


On a side note, if you are going to be making planters, think about tackling a “planter project” in the fall or winter. You will have ample time for a proper curing and you can put it outside to leach naturally. Your planter will be ready by spring and you’ll not have lost any valuable growing time.

As with all hypertufa projects … experiment to find what works best for you.

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