Concrete Countertops FAQ

Dear Friends,

Thank you for submitting so many thoughtful, insightful questions about concrete countertops during our Ask the Author campaign. Below is a sampling of questions I have had the opportunity to answer for you. I hope you will find the answers and information useful in your pursuits to design and build creative concrete countertops. Thank you again for your support.

Yours,

Fu-Tung Cheng

Drying problems

Q.  In the drying process, I'm having problems with the tops curling. Do you know what I can do to combat this?

A.  If you are pouring thin (under 1 in. to 1-1/2 in.) and curing too quickly, this could be the problem.

Achieving a smooth finish

Q.   What is the best way to achieve a smooth finish on a countertop that has been poured in place?

A.   Screed the piece with absolute precision, and have an expert trowel the surface. Timing and "feel" are critical in getting a flat, smooth finish. If you are going to grind lightly and polish after the concrete has cured sufficiently (3 to 4 days or less, depending on your cure time and mix design), a flat surface is imperative to avoid tedious grinding to even out the surface.

Topical vs. penetrating sealers

Q.   I've read many articles about concrete countertops, and they are all full of details until it comes to sealing the material and applying the final finish. It seems anyone can build a concrete countertop, but the final steps are magic. Can you please help us do-it-yourselfers so I can finish my kitchen?

A.   There are two basic approaches to this (imperfect) process: topical sealers, which effectively seal off the surface completely, and penetrating sealers, which seep into the concrete and can be finished off with beeswax or carnuba wax to leave a "natural" feeling surface.

The advantage of topical sealers such as epoxies and urethanes is that they truly are stainproof. But there are disadvantages, too. Topical sealers are difficult to apply evenly without sophisticated spray equipment (including environmentally proper ventilation equipment). They can, in time, "lift" from the surface if there is any trapped moisture in the countertop, and then are very difficult to strip and remove without the use of toxic chemicals. Topical sealers can have a "plastic" feeling -- sort of defeating the sensual aspect of the polished concrete surface. Finally, a plastic surface cannot tolerate high heat.

Some fabricators who favor topical sealers sometimes dull the offensive "plastic" look by steel-wooling the finish. This method assuages initial client objections to staining in the short run, but I feel in the long run it may disappoint the end user if problems develop with the finish.

Penetrating sealers are easy to apply, are acrylic or silicone based, and are generally nontoxic. The problem is that they don't work very well in repelling the deleterious effects of acids from lemon juice, vinegar, and red wines that work on the lime (base) inherent in concrete. At best, they delay the onset of "etching" that occurs when an acid meets a base. With a coating of wax, they essentially buy a bit of time for one to wipe up the offending substance.

Using penetrating sealers means accepting the premise that the concrete can and will develop "character" and "patina" over time, but at an acceptable level. Much as a wood floor, though less practical than a floor of granite tile, is often favored because of its warmth and sensual qualities, so a concrete countertop, if designed with all of its advantages of sculptural practicality, can earn the same level of acceptance for its vulnerabilities by its virtues.

At Cheng Design, we have learned from our clients and have found that balance between the practical and the aesthetic: penetrating sealers and waxing periodically (once a month) is the best method to maintain the countertop for many years. In five to ten years, if required, the entire countertop can be given a light polishing, and voila, it looks almost new again. This process is explained and illustrated in my book, Concrete Countertops.

Remedy for a flawed topical finish

Q.   I recently put in concrete countertop myself (hiring out pouring and finishing only). I used Staincrete Acid Stain, followed by Increte Clearseal, an acrylic sealer, and their wax. I’ve had the counters for only a month, and we’ve got problems. The stain has developed dark spots, like some sort of skin disease; the countertop are chipping (if I drop a butter knife from 6 in. up it’ll chip); worn areas are appearing where we use the countertop the most; and there are areas of uneven sheen (which we could probably get rid of with more wax).

What should I have used for stain or for a finish that might hold up better? Given what I have already done, what should I do now to improve the durability and even out the color? Can I take off the acrylic sealer, and if so what should I use in its place?

A.   You have outlined the reasons I avoid topical sealers. Follow the manufacturer's recommendations for stripping the acrylic off (usually it takes a nasty chemical ). In the past, we have simply scraped off the finish with razor blades, then applied the nasty stripper, flushed and nylon padded the surface, then applied a penetrating sealer and wax.

What to do about unacceptable staining

Q.   We recently made and installed a concrete countertop in our home. We mixed 60% sand and 40% portland cement, some grey pigment and added Xpex, an anti-hydro agent. After wet-curing the slabs for two weeks we took them out of their forms, sanded them down, used water-based penetrating sealer called Stonetech Professional Porous Pro (because my wife is pregnant I didn't want to use their oil-based version) and then waxed them with Trewax clear paste wax. We love the countertops except for the level of staining we are getting. We expect them to stain (the worst is citrus). I read in your book about the process of refinishing the counters but I still have questions:

• Do you recommend a specific penetrating sealer (we are trying to avoid extremely toxic products that are full of things like xylene)?
• Should I be using an oil-based version?
• Do you recommend a particular wax for countertops?
• Do you have any general recommendations for reducing the level of staining? Perhaps my mix is at fault.

A.   Thanks for asking this question!

Unfortunately, the ideal penetrating, nontoxic, stainproof sealer does not exist. Believe me, we have tried every offering out there. I am always hopeful, but often have been disappointed in the claims from many of the manufacturers. I suspect that because of the crystalline structure of the perpetually curing concrete, minute pathways are constant from the surface into the matrix of the lime-based material. We prepare our clients to accept a certain amount of incidental staining. Those who have their counters waxed monthly and are careful to wipe off spills of the offending fluids reasonably quickly, are content with the balance between the beauty and the maintenance. Most the kitchens by Cheng Design don't place our counters in a relentless monotony as though they were wall-to-wall carpeting. We design them to be major accent and focus pieces, functional sculptures to be complemented by other materials such as granite, stainless steel, and tile.

Acid stains

Q.   Why didn't you cover acid stains in the book? Is there a reason why you stay away from them?

A.   We have avoided acid staining in countertops (we used the technique on floors and walls extensively at one time) because of their composition of heavy metals. There may be a health risk. After I had personally washed many floors with the acid washes, I found out heavy metals are used to create the stain. When I called the manufacturer, I learned that all washout rinse residue had to be taken to a hazardous waste disposal site. This was not conveyed on the instructions, and many contractors simply wash and rinse into the ground this potentially grievous substance. So I have cut back on my use of this effective technique.

Achieving a terrazzo effect or a streaky finish

Q.   Do you have any tips about adding inlay materials (broken glass, for example) into the concrete to get a terrazzo type effect? I'd also like advice on creating a streaky swirled finish. Can you add pigment to the mix and stir it completely, like making a marbled cake?

A.   You can add broken glass as an additive to the entire mix, as though it were another aggregate, or simply scatter an amount at least 50% more than you want to show into the mold form before the pour and simply pour over the material. Much of the glass will migrate away from the bottom of the mold, especially when you vibrate the mix. Sometimes we mix a little water-soluble white glue in with the glass before scattering it into the bottom of the mold. When the glue sets, the glass, now stuck on the bottom face of the mold, will not be able to migrate during the pour, so much more of it will appear on the surface of the countertop when we start grinding the surface.

A streaky or swirled finish is easily accomplished by placing concentrated patches of colored concrete onto the mold and letting them stiffen a bit before adding the bulk of the mix. Vibrate carefully, so as not to reintegrate or homogenize the separate batches together.

Grinding and polishing sequence

Q.   How do you achieve a high polished look?

A.   One can achieve a high polish by grinding carefully with diamond pads -- first 80 grit, then 120, 220, 400, 800, 1200 and 3000 -- just as marble and granite fabricators do. Concrete is a lot softer than granite and will take a polish much quicker. A short cut is simply to go from 50 grit, to 120, to 220, and end with 400, and let the wax at the end give you the polish when it is buffed out.

Avoiding glare

Q.   Using your method, how can I avoid glare where I construct interior concrete windows sills in my straw-bale home?

A.   I suggest that you avoid grinding and polishing too much and simply leave a slightly rougher finish.

Staining after the cure

Q.   Using your method, will the concrete accept a penetrating stain when applied after the concrete has cured?

A.   Yes. No matter how smooth, the concrete is still absorbent enough to accept a penetrating sealer and /or stain after it has cured.

Unground and unpolished?

Q.   Do you always grind and polish every piece?

A.   Not necessarily. If you like the results straight out the mold, then don't do any further work.

A cure for efflorescence

Q.   How do you keep the countertops from surfacing the efflorescence to the top and creating a milky white finish. I have 3,000 square feet -- yes, 3,000.

A.   Efflorescence is one of the mystery diseases of the concrete world. Its causes and roots are often the subject of professional journals.

Unfortunately, this is a very difficult problem to solve. Somehow moisture is forcing excess, free calcium to the surface, and will continue to do so as long as moisture is present and there remains free calcium in the concrete. The only ways to combat this problem are to force more moisture on the piece (i.e., wash, or flush) until all the calcium has leached out or to prevent any moisture from reaching the piece to begin with.

Filling voids

Q.  In my countertop I have a few small voids (created by trapped air). What is the best way to fill those voids?

A.  Voids are best filled with a slurry coat of pure cement and fine or no sand. See my book for specifics.

Attaching concrete countertops to cabinets

Q.   How do you fasten the concrete countertops to the cabinets?

A.    There are a variety of methods depending on the conditions in your area. For instance, in the San Francisco Bay area, earthquakes are a real threat, and we like to secure the countertops with threaded rods in cases such as freestanding island tops. In most cases, however, especially where we feel the countertops have little possibility of movement, we simply glue them with construction adhesive and use concrete screws such as Tapcons to fasten them to the cabinets from underneaths.

Food-grade sealers

Q.   What is your favorite food-grade sealer for concrete countertop?

A.   There are many companies offering penetrating sealers -- Aqua-mix, Brightstone, Phenoseal, Miracle 5000, Glaze-'N-Seal, to name a few. Please refer to the manufacturer for a Material Data Sheet for the best application around food. Most of these products are benign, but I avoid the solvent-based sealers for food situations.

Bacterial contamination

Q.   How is the issue of microbes and bacteria penetrating and breeding on the porous surface of concrete addressed?

A.   To the extent that a polished and waxed concrete piece has the porosity of marble, I can only say that bacterial contamination hasn't been a big consideration of mine. However, I am sure there are experts on this subject who are far more qualified than I to argue the merits and shortcomings of concrete.

Countertop care

Q.   What can you tell me about the care and cleaning of concrete countertops? What colors can you do?

A.   Washing with mild soap and water is the best method of cleaning. We always use integral concrete pigment to color.

Liquid vs. powdered pigments

Q.   What is your approach to adding coloring agents to concrete? Are there some agents that someone might think would work but that should be avoided?

A.   There are both powdered pigments and liquid pigments (usually just the same but in a suspension of liquid). Both are fine to use. If you prefer a more uniform look, the liquid is more efficient. If you are seeking a slightly mottled look, use the powdered form and “fold” in the color rather than thoroughly mix.

Getting the look of limestone

Q.   How would you simulate soft gray limestone with subtle pint streaks?

A.   Experiment, experiment!

Concrete color and sunshine

Q.   Will concrete color hold up well in the sunshine?

A.   Most iron oxide pigments are color fast, including the reds, yellows browns, oranges, and blacks (synthetic black oxide is more color fast than carbon black) The greens are a bit more elusive, and blue (except for the very expensive cobalt blue) is very unpredictable when subject to UV rays.

Wood and concrete

Q.   I heard from an Andersen Window rep that it is unwise to have wood touching concrete. (He went on to say that they use a special compound between the wooden window frame and the concrete of the building – a poured concrete high rise.) This sounds like conventional wisdom to me, and I nodded solemnly as he said this. Then on the cover of your book I espied a very nice countertop that has a large wood piece on it. Are there problems in having wood touching? If so, how do we work around them?

A.   Yes, you are right to question his application of conventional wisdom to this case. He is talking about foundations and structural concrete passing water and moisture to the wood, giving rise to dry rot or wet rot. But in the interior use of concrete there is little chance of inclement weather. The cutting board in the photograph is fully removable and should be air dried periodically.

Silicone releasing

Q.   I've been using a silicone caulk for the bottom of my precast forms, but when I pull the countertops, the silicone always seems to "keep" some of the smooth portland that would normally make an awesome smooth edge. I use a typical oil-based form release (the same release they use for commercial construction) and apply it with a small paintbrush. Am I doing something wrong, or is it just part of the process?

A.   We have never had a problem with silicone releasing. Perhaps try a different brand of high-grade silicone and make sure you "tool" it only once...so as to not create "wrinkles" in the silicone.

Concrete counters in professional kitchens

Q.   Would concrete countertops work in a professional kitchen? Are there easy to clean and sanitize? Are there worries with applying surface coating? And finishing in this application (wear and flaking).

A.   Check with your local health department official. In California, at least, concrete counters are allowed in food service, if not prep, areas.

Cracking

Q.   What do you do to prevent cracking, and what, if anything, do you do to repair cracks?

A.   Good mix design and proper curing are the keys to prevention. The subject is too involved to cover here. Please read my book.

Concrete sink

Q.   I want to make an under-mounted concrete sink. How can I attach the sink to the countertops? Also if I were to form the countertops and sink as one continuous piece, how should I reinforce the union between the sink and the counter?

A.  Whew! That will be a heavy sink. I would reinforce from below rather than simply hang. You might try to form a "key" to attach the two pieces.

posted 5/17/2002

Finishing countertops in place

Q.   If you pour the countertop in place, then how bad is the dust problem when you finish them? We have two children and are concerned about the dust, especially since my wife wants soapstone blue countertops with the more toxic blue pigments.

A.  We usually wet-grind, so dust is not a problem. However, the mess can be.

Concrete over an existing countertop

Q.   Is it possible to build a form around existing countertops and pour concrete directly over this surface?

A.  Yes, that technique is covered in the book.

Integral sink and countertop

Q.  Have you ever done molding with integral molding of sinks with the countertops? I have several ideas in the paper doodle stage and would be interested in your thoughts.

A.  Yes we have, occasionally. And many other fabricators have as well (see the book for examples). My only reservation is that constant water flowing from the faucet to the concrete surface will inevitably erode the top "cream" layer of the sink at that spot. That's why I favor using stainless-steel sinks. That said, as sculpture, nothing beats a cast, integral sink for looks.

Recipe for a mix, and ways to lessen its weight

Does your book answer specific questions as far as mix is concerned? Will your book give me at least one good mix that I can use to get me started? There are ways of making concrete lighter in weight -- do you know what those are?

Yes, of course we specify a mix design. It is a very good base recipe to start. You may want to tweak the recipe, but there won't be a huge deviation from this foundation recipe unless you start experimenting with lightweight aggregates or other additives. Lightweight aggregates include: expanded shale, pumice, vermiculite, and glass. One can also use sprayed-on fiberglass-reinforced concrete to minimize thickness and maintain structural integrity.

Working with ready-mix

Q.  What is the best way to mix the concrete? If the project is large enough, is ready-mix a choice?

A.  Yes, ready-mix with a pumper is a great way to go. The book explains the intricacies of working with the dispatcher to keep your mix from going south.

Unsupported overhangs

Q.  Our property owners association is planning to build an open-air community center. We have decided to use concrete countertops on two counters, one 20 ft. by 5 ft. and the other 20 ft. by 4 ft. with a stone front and sides. How much counter overhang can we have on the larger unit, and what type of permanent support framing will we need if we make the tops 4 inches thick?

A.  If you mean countertop overhang for leg room, I suggest 14 to 16 inches. If you mean cantilevered overhang, consult an engineer. A 100-sq.-ft. slab of 4-in.-thick concrete is no joke. I would suggest asking an experienced cabinetmaker or engineer to calculate the support you need.

Q.  For an island countertop, on the "eating"or non working side (with stools pulled up to it), how much unsupported overhang is feasible?

A.  It really depends on the amount of reinforcing, the attachment to its support, the thickness and weight of the slab.

Specs for a bathroom counter

Q.  What is the thinnest that a concrete surface can be for a 5-ft.-long bathroom countertop? And if later you want to change the cabinets, they what?

A.  Depending on your skill and experience a counter can be as thin as 3/4 in., but for novices I would recommend nothing under 1-1/2 in. Change the cabinets first!

Durability and appearance

Q.  How do concrete countertops compare to laminate or solid surface countertops? What about durability -- can they handle hot pot from the stove,? What about red wine. What about chipping and cracking?

A.  The book discusses in detail the relative merits of concrete vis-a-vis other materials for countertops.

Concrete vs. marble and granite

Q.  What are the advantages of concrete over marble and/or granite?

A.  The biggest advantage is the ability to sculpt, mold, and inlay the concrete. There is also the advantage of being able to do the work yourself.

Ordinary premixed concrete should be avoided

Q.  Is it possible to use premixed concrete bags from any hardware store that include pea-gravel in the mix, subsequently vibrating the mix and adding color? Will the outcome be the same as far as the finish is concerned or will there be significant differences from using your recipe?

A.  We don't recommend using ordinary premixed concrete bags because the material is usually of uneven quality. The use of higher-quality premixed sacks of concrete such as Quikcrete 5000 is highly recommended, especially in conjunction with our Neomix kit.

Sealers

Q.  Please recommend sealers, specific suppliers, manufacturers and products. I understand USDA-approved products for food prep are available -- what are these products?

A.  Please refer to References in the book. Check the specific manufacturers' Material Specification and Data Sheet (MSDS) for toxicity data and suitability for food prep areas. Generally there are urethanes and epoxies that are topical finishes approved by the USDA. The penetrating sealers have to be looked at individually for safety's sake.

"Vertical" countertops

Q.  Can the techniques in your book be adapted for vertical surfaces? I would like to do bathroom walls and a shower surround with a similar look and feel.

A.  Yes, especially if you decide to pre-cast. Essentially one is making large "tiles."

Outdoor applications

Q.  Would concrete countertops be good for outside use, say, in a pool area as a grill surround and/or serving counter? How about window sills?

A.  Outside use is possible, but one needs to address freeze/thaw and efflorescence problems. Tricky.

Veterinary applications

Q.  I need to build concrete cabinets and sinks that are beautiful and functional for a vet's medical kennel area. Is this feasible?

A.  I don't see why not.

Do try this at home

Q.  Is concrete countertop work a do-it-yourself project or must it be professionally done to look so beautiful?

A.  Nice work can be done by amateurs. Much of the work you see in the book is the result of years of experience, but don't forget that the first large piece I poured in my own house has been the model for many a feature article from House Beautiful to Fine Homebuilding over a 15-year period!

Concrete fireplace facade

Q.  Can you create a fireplace facade?

A.  I've done it many times.

Preventing cracks in a concrete sink

Q.  How would you alter your process and/or mix to pour a concrete sink so that the corners do not crack through to the outside edge?

A.  This seems to happen when water is left in the sink for any amount of time. The problem does not seem to be related to rebar or the size of the sink, but to the fact the water is being introduced to the function of the finished product.

What about floors?

Q.  Can you use the same method to create floors?

A.  Yes, but floors have their own requirements, such as curing methods, reinforcing, and placement. Essentially, though, it is a similar process.

Checks and cracks

Q.  How can I control checking" in the surface? Without some viable method to ensure a smooth, undisturbed surface, this cracking (however small) will make concrete countertops and sinks an unacceptable design choice for many home buyers. Have you found a solution to this problem?

A.  We actually welcome "crazing," but what you are describing may be a failure of the mix. Of course, with concrete, some occasional hairline cracking is inevitable. Larger cracking is usually caused by mishandling or stressing during transport and installation, structural stresses on inherently weak areas such as around sinks and faucet knockouts, or spans that exceed the tensile strength of the reinforced concrete.

posted 5/6/2002

Preset vs. cast-in-place

Q.  I see the book covers how to preset a concrete countertop. It looks great in the photos. However because of the size of my future island countertop, I was considering cast-in-place. Is that covered too, or do you consider cast-in-place to be a bad idea?

A.  Cast in-place technique is covered in the book in the last chapter. The two main limitations are the lack of detail possible with top troweling and the difficulty in elevation changes (which limits design possibilities). Even if you wish to grind and polish in place after the piece has cured, it is inherently more difficult because the surface is not as flat as when pouring into a flat mold. You end up grinding much more of the surface away to get a even look.

Joints and edges

Q.  How do you join the countertops when it is built in sections? If you do not pour right side up how do you get the nice bull nose edges?

A.  In the book we use the simpler technique of an aluminum divide. A more sophisticated approach is to shape the metal divide into a Z shape to act as a key between the two sections. Another way is to affix a half-dowel on the metal divide to act as the key. Bullnose edges are accomplished many ways, none of which are very easy. We have formed them by building up a plaster edge with a shaped edging tool (made from sheet metal), then smoothing and coating the plaster with shellac, we have heat formed plastic mylar and laminate to form the edge, and we have used foam shaped edges.

Secrets of secrete?

Q.  In limited space secrete is the most convenient mix but it poses a few problems. First, the finish on secrete seems to remain dusty regardless of how much it is cleaned. Second, the properties of the "cream" seem to make it difficult to finish (poured in place). Are there additives on the market that can abate either one of these problems? Your recipe for a pigmented concrete slurry includes two major ingredients (calcium carbonate/cement and pigment) the same ingredients as slurry. By the same token can colored grout be used to fortify/color a concrete mix?

A.  Sorry, but I'm not familiar with "secrete." You certainly are welcome to try my Neomix kit (to be released in late May 2002), which includes every additive you need to fortify pre-bagged concrete available at most hardware stores to a quality suitable to use for a countertop. The kit also includes pigment, diamond and carborundum polishing pads, sealer, wax and complete instructions on how to get started right away without having to pre-measure separate materials such as graded sands, cement powder, plasticizer, fibers, etc.

Pros and cons of off-site casting

Q.  Are concrete countertops all made off site in a mold and then brought to the site for installation or can they be made on site? If they are fabricated off site how heavy and how fragile are they to move?

A.  As the book explains in more detail, there are advantages and disadvantages to each method. I favor off site casting in mold because of the design and sculptural potential. Yes, they are heavy and fragile until secured into place. Handle like glass!

Polishing and staining

Q.  I purchased and reviewed your book on Amazon. I think it’s a great book, thanks. My experience with concrete is limited to pouring a driveway and some footings for a deck. I plan to build only one countertop for a home I'm building (maybe two if things go horribly wrong) I have several questions:

• Are there any alternatives to the expensive diamond abrasives you used for polishing in the book?
• Would acid stains be affective way to add color and visual interest to a countertop? What are the advantages/disadvantages?
• Your book said that you would be offering ready-to-pour mixes on your Web site. I visited and found nothing. When will these be offered?

A.  Yes there are carborundom pads available, but they wear out much quicker than the diamond pads. A cost-effective method is to use the diamond pad (80-100 grit) to cut the surface and the carborundom pads (150-220+) to finish and polish. These pads are included in our Neomix kits (available on www.chengdesign.comin late May).

Acid stains are a very effective tool for color effects on concrete. Remember, however, that they contain heavy metals, and any runoff from your working with them is detrimental to our environment.

Sources for inlaid natural stone and premixed color

Q.  How do you get the inlaid natural stone as shown on page 31 of the book? Also, how can I order the premixed color (blue-gray) that is featured in the book?

A.  I find my inlays at rock shops and from rock hounds. The blue grey is a blend of grey cement, ultramarine blue, and a hint of black oxide. That particular color is available in the Neomix kit (available on www.chengdesign.comin late May).

Concrete backsplash tiles

Q.  I would like to make some concrete tiles for my backsplash to match my countertops. Can you suggest a mix for tiles?

A.  Great idea to start with tiles before graduating to a countertop! It will give you a chance to get a feel for what you are doing before committing to a large mistake. Use the same basic recipe in the book.

Source for Geocrete in Arizona

Q.  I can't find a dealer in Arizona that carries Geocrete -- can you update your list or send me a list? Also, I'm interested in pouring some different colors/ textures than your recipe Geocrete and wondering if you would be willing to tell me the recipe for a good concrete mix -- especially in regard to rein enforcement (i.e., fibers) used within the mix to minimize cracking.

A.  Please read the book on the mix question. Geocrete is a product by Cheng Design that we sell to the high-end kitchen dealer. Dorado Designs of Tucson is one of our dealers in Arizona.

Advice for would-be countertop entrepreneurs

Q.  I just bought the book and love it. I want to start a business doing countertops and other products made of concrete and after reading the book I feel 500 % more confident. What advice do you have for starting this kind of business in an area that has no other competition in this field? Thanks for a great book like this.

A.  Start modestly. Gain experience at a measured pace. As a business, it is not as easy as it looks. Educate, as well as inspire, your clients. Manage their expectations, and you will save much grief. Develop and innovate a look and feel, a style, if you will, that motivates you, and in turn your vision will motivate the client. Explore the full potential of the medium, and study good design!

To learn more

Q.  How difficult is it to master the craft to the level of quality necessary to go into business? Any other reference ideas would be greatly appreciated.

A.  See my answer to the previous question. For more information, take a look at www.concretenetwork.com, the Portland Cement Association Web site (www.portcement.org), and the monthly periodical Aberdeen's Concrete Construction (426 S. Westgate St., Addison, IL 60101; 708-543-0870).

What do concrete countertops cost?

Q.  What are the price ranges to customers for concrete countertops?

A.  Go to www.concretenetwork.comfor many listings of fabricators and their pricing.

Cheng Designs on display

Q.  Where can I view some samples of your work? I live in southern California.

A.  Studio Becker Kitchen Showroom at the Pacific Design Center in West Hollywood has one of our Geocrete products on display. Our Web site is www.chengdesign.com.

Concrete vs. granite

Q.  I have been debating about granite countertop for our kitchen. We like the material but are stopped by the high cost. How does concrete compare to granite in both cost (per sq. ft.) and texture?

A.  With concrete, if you do the work yourself, you can have fun, be creative, and save huge sums of money. If you have someone fabricate a concrete countertop for you., it is as expensive at this time as granite, mostly because of high labor costs.

Concrete countertops for non-millionaires

Q.  I love the look, but I want to do a middle to lower-end kitchen. Is this possible? I love doing home-improvement projects, and if the price is right vs. Corian, then I can put my money elsewhere. All I see are these multi-million-dollar kitchens. What about the rest of us?

A.  I am so glad you asked. The reason I wrote the book was not only to inform and educate professional designers and architects, but also to inspire everyone to have some fun and be creative. So much is specified and manufactured for our consumption. Why not take a breather from consuming and start re-creating our own environments? Aside from tile work, there aren't many kitchen projects that are feasible for a homewowner to make and personalize.. Concrete countertop work is certainly is one of them.

The idea of making a kit available to the public came about because I realized that it would be very cumbersome to assemble all the materials I specify in the book to create a mix. Most of the ingredients are not available to the general public, they are for professionals and come in amounts that are simply too large. So rather than having to gather cement powder, gradated sands and aggregates, then measuring and weighing them, we designed the kit to be used with high-quality sacked, or bagged, concrete available everywhere in convenient 60-lb., 1/2-cu.-ft.-sized sacks. Each Neomix kit contains everything you need to pour, grind, polish, and seal a countertop approximately 2 in. thick 25 in. deep by 8 ft. long (using 6 sacks of Quikcrete 5000, for example). We calculated that a simple countertop this size would cost from $600 to $750 to make, including the kit, the mold materials, renting a mixer, grinder, and vibrator, and a six-pack of beer for the help you'll need lifting the piece off the table.

Two questions on skill level

Q.  On a scale of one to ten, with one being an inexperienced person, and ten being a general contractor w/years of experience, how difficult is it to make a straight-line kitchen countertop, a sink cutout, and a curved-edge countertop?

A.  A simple straight countertop would rank between 1 and 3, a sink cutout 3-4, and a curved edge 5-7.

Q.  What kind of working knowledge is required to do a countertop?

A.  None. We tested our Neomix kit on complete novices and they successfully completed some beautiful tops without prompting by simply follow our shake-n-bake instructions.

Concrete potting bench?

Q.   Would concrete countertops be an excellent choice for a potting bench? Is a project that most folks with average skills can undertake?

A.  Absolutely.

Local installers and dealers

Q.  Where can I find local installers and professional contractors? Where can I find local dealers of Geocrete?

A.  For professional installers, see www.concretenetwork.com. For Geocrete dealers, see www.chengdesign.com/dealers.html

A traditional look

Q.  Do concrete countertops have an application in more traditional kitchens?

A.  Yes. Style is dictated by design. Concrete can adapt to any look.

Durability, staining, and maintenance

Q.  I am concerned about durability, staining, and maintenance. Does concrete need to be regularly maintained in any way? How does it hold up to things like red wine, turmeric, beets and other things that stain. Can you put hot things on it with no problem?

A.  Read the "Vulnerablites" section of the book on staining and sealing questions. Hot things are generally not a problem.

Premixed concrete?

Q.  Is it possible to use premixed concrete bags from any hardware store that include pea gravel in the mix, subsequently vibrating the mix and adding color? Will the outcome be the same as far as the finish is concerned or will there be significant differences from using your recipe?

A.  We don't recommend using bags of ordinary premixed concrete -- it is usually of uneven quality. We do highly recommend the use of higher-quality premixed sacks of concrete such as Quikcrete 5000, especially in conjunction with our Neomix kit.

To grind or not to grind

Q.  In your book you discuss the need for grinding the concrete once it is out of the mold, but on your Web site you say that when you make a countertop grinding is not necessary. Please explain.

A.  Lightly grinding and polishing is the preferred method of nearly all concrete countertop fabricators because of the ease of correcting the myriad defects and aberrations that can appear mysteriously on the surface of a freshly poured countertop. Cheng Design's proprietary process for consistently producing tops without defects is tedious and not practical to convey; that is what gives Geocrete it special quality.

Silica fume, Scofield admixtures

Q.  Have you tried silica fume (powder form) for more strength? Have you tried Scofield admixtures with any success?

A.  Yes, to both questions. There are many avenues to explore with mix design, each gives a different look and feel the final product.

Source for ultramarine blue

Q.  I just bought your book today after reading the article in Fine Homebuilding. Thank you. In the past I have tried to find ultramarine blue but haven't had any success. What's your source and how much should I have to pay?

A.  The book lists Conrad Sovig (35 Gilbert St, San Francisco, CA; 415-863-3808) as a source for ultramarine blue. I'm sure there are others in your area. Expect to pay anywhere from $4 to $6 a pound.

Where to buy the book Concrete Countertops

Q.  Is your book sold at major book stores?

A.  Yes. It is also available online at The Taunton Store.