Cost-Cutting Techniques in Stone Bathtub and Sink Production:  What to Avoid

Lux4home™: A Guide to Choosing Quality Stone Bathtubs and Stone Sinks

We have been operating in the stone industry for over 20 years, with some of our employees having over 30 years of experience. During this time, we have gained immense and invaluable knowledge in the field of natural stone, which we officially share through training sessions for new craftsmen in Indonesia, representatives of importers, or through courses for bathroom fixture shop owners. These courses cover how to properly manufacture stone bath tubs and sinks and how to purchase stone baths and sinks. We are not afraid of new competition because no one can turn back time to make up for our 30 years of experience.

We share this knowledge because, each year, many people and companies fall victim to purchases from unreliable suppliers. This often results in a desperate search for technical support and problem-solving assistance, leading them to us. When it turns out that these issues could have been avoided at the order fulfillment stage, we recognize once more the need for this guide.

If you are an individual customer interested in a bathtub or sink made from any kind of stone, we want to share this knowledge with you now – before your purchase, not afterward, when problems may arise. No one is an expert in everything, so you don’t have to know how to properly produce stone items that will be durable for many years, not just for a short time after purchase. In this guide, we describe real cases brought to us by clients of other companies, other importers, or users who received no support from their suppliers. Their products either couldn’t be used, repaired, or lost their functionality within a year of purchase. These were people reaching out for technical help, advice, or problem-solving.

We will not present cases that happened only two or three times but ones that were repeated many times. For some, this information will be valuable; for others, it may be problematic, as it might require changes in their production or could lead to the loss of informed customers. If any of the points don’t apply to you, feel free to skip them and move to the next one you find relevant. Keep in mind that this guide is aimed at various groups.

If you are considering purchasing these products from us at Lux4home™, you don’t need to absorb this information, as it is part of our standard practices—unless, of course, you find it interesting.

Ways to Lower the Price of a Stone Bathtub or Sink During Production and Their Consequences

In porcelain cup manufacturing, cheaper cups are made by reducing firing time, which lowers energy costs but also makes them less resistant to impact and prone to releasing harmful substances. Similarly, in the production of stone bath items:

• Method 1: Shortening the polishing time of the inner surface. The manufacturer saves a substantial amount of power for machine operation and reduces the labor hours required for workers.
  • Consequence: Increased stone absorbency, as the material absorbs water used in the sink or bathtub. The stone becomes much heavier, stays constantly damp, may leak, and stains easily.
    
    
    
    
• Method 2: Using polishing and gloss-enhancing pastes that are not certified for skin or food contact or have not been tested. This saves the manufacturer from purchasing expensive, certified materials.
  • Consequence: Harmful substances are released into the water with each bath, posing a health risk.
    
    
    
    
• Method 3: Ignoring the selection of stone based on veins and micro-cracks. The manufacturer avoids sourcing another stone block and uses all available stones, regardless of flaws.
  • Consequence: Water seeps through the stone, leading to further cracks in the bathtub, making it unsuitable for outdoor use.
    
    
    
    
    
    
• Method 4: Filling holes, cracks, crevices, and chips in the stone with putty or glue. The manufacturer doesn’t need to source a new stone block, using each block regardless of damage.
  • Consequence: Artificial fillings will almost certainly fall out within about a year, exposing the true surface of the stone.
    
    
    
    
    
    
• Method 5: Neglecting details like the drain, water flow, or surface quality. The manufacturer saves worker time since they don’t need to spend as long on a single bathtub.
  • Consequence: The bathtub’s plumbing beneath may prove impossible or very difficult to install, often only discovered upon receipt and installation.
    
    
    
    
• Method 6: Using overly powerful hammers or tools that cause excessive vibrations. The manufacturer speeds up the stone bathtub production process.
  • Consequence: The hammer causes numerous cracks and micro-cracks, often revealed only after prolonged contact with water and the strain of filling the bathtub with water.
    
    
    
    

Now you know how the cheapest stone sinks and bathtubs are made.

Many realize this only after the fact. Here are just a few examples from customers who approached us for technical support—after the fact:

Customer Case 1 (*Click to enlarge)

Customer Case 2 (*Click to enlarge)

Customer Case 3 (*Click to enlarge)

Customer Case 4 (*Click to enlarge)

How to Buy Stone Bath Tubs and Sinks / How Not to Import Stone Baths and Sinks

Strive to ensure as many of the following points as possible when buying from another producer than Lux4home™:

Avoid these cases:

Stone Bathtub and Sink with Micro-Cracks or Cracks.

A. Micro-cracks and cracks may appear when the material hits another stone block. This can happen:

1. In a river—if these are river stone sinks or bathtubs, rapid water currents can cause stones to roll with the current (such stones should not be collected, yet some do not want to forfeit the effort of locating such stones).
2. During the loading or unloading of stone blocks for production (such stones should not be processed, but some prefer not to bear the material loss and knowingly produce items from them).
3. In the final stage of hollowing out the sink or bathtub interior when the walls already have a visible shape. At this stage, the stone is weakened, and an accidental impact may cause an entire wall to crack. Similarly, improper production methods using hammering tools (faster production at the expense of quality) lead to micro-vibrations and material detachment.

When Do Cracks and Micro-Cracks in Bathtubs and Sinks Typically Become Noticeable if They Aren’t Identified Earlier?

Unfortunately, cracks often reveal themselves only after the bathtub is filled with water, left with water inside for an extended period, or after repeatedly washing the sink or bathtub—when masked cracks are washed out, possibly concealed with wax by unscrupulous sellers to hide them at the point of sale. In most cases, this happens when the bathtub is already far from the production site, making returns impossible.

Consequences of Receiving a Sink or Bathtub with Visible or Hidden Cracks

If the problem involves a stone sink with micro-cracks, it may still be usable for a while as long as it’s not filled with water with the drain plugged and the crack is on the side wall of the sink. However, larger cracks or micro-cracks at the bottom of the sink will cause it to leak, and even accidental knocks could result in a break.

In the case of a stone bathtub, cracks or micro-cracks have far more serious consequences. They can lead to the bathtub leaking completely, soaking through, and certainly causing cracks to worsen. If the bathtub is installed outdoors in climates with freezing temperatures (as we discussed here: “Stone River Bathtub Outdoors – Tips & Tricks“), it may not survive one season. If installed indoors – in a bathroom, SPA, or other location – use should be stopped immediately. There is a risk that the crack will enlarge quickly and unexpectedly, causing the bathtub to break. This is due to temperature fluctuations in the stone, water pressure, the weight of a person using the bathtub, or vibrations. Before this happens, the bathtub may leak, and the crack may absorb moisture. This situation poses a risk to the user as well as to the owners of the room where the bathtub is located. A complete break in the stone occurs suddenly and very quickly. 

How to Repair a Cracked Stone Bathtub or Stone Sink

If the crack hasn’t caused the sink or bathtub to completely split and it’s still in the form of a crack, assess the size of the crack. Try consulting with a local stonework company in your country. They should have knowledge of adhesives or epoxy resins specifically for natural stone. Avoid attempting to seal the crack on your own if you are not a specialist. Depending on the type of crack, you can try filling the gap or micro-crack with a specialized resin, selecting the viscosity to match its depth and width. In some countries (e.g., in Europe), very thin resins are available (like water) that allow for filling micro-cracks and sealing the damage. However, the surface will need to be polished again afterward. Additionally, repairing cracks in a horizontal area of the bathtub or sink is usually easier than on a vertical wall (filling with liquid is simpler in these cases). However, there’s no guarantee that such measures will succeed or that they won’t need repeating. Your supplier should not have sent you a product like this!

B. External Damage

External damage to stone bathtubs and sinks can be categorized into:

• External damage to onyx, marble, or granite bathtubs and sinks where scratches or chips appear on the regular, polished surface. These could have occurred either before production started or after it was completed (e.g., during polishing, packing, or loading into the container).
• External damage to river stone products, where the structure is unpolished. Here, damage becomes visible during raw material extraction from the river and should not be continued in processing.

• External damage during packing or transportation. Often, nails protruding from packaging cause scratches or chips, and poorly selected or bulk packaging contributes to these issues.

   

When Damage Becomes Noticeable?

Claims of product quality at the time of shipping are always identical. Without overseeing production to the very end, you can never be certain what will greet you when you open the crate containing the sink or bathtub at the final destination. A missing broken piece (like in a puzzle) within the packaging upon unpacking indicates that the damage occurred before transport.

Consequences of Receiving a Bathtub or Sink with External Damage

There is certainly an aesthetic concern, and it is undoubtedly a financial issue – some agents or sales intermediaries take such products for free, as waste, and resell them as fully functional products, resulting in the customer paying for what is essentially a defective item. However, the most significant consequence of receiving such a product is the disappointment, and there is usually nothing that can be done at this stage. It is also important to know that a damaged external section has different absorbency and moisture absorption than an intact section, so take care not to expose it to moisture.

How to Repair a Scratched or Chipped Stone Tub or Sink
Before taking any action on your own, contact a local stonework company in your country that specializes in natural stone. For products with smooth surfaces, you can attempt to mix clear epoxy adhesive with dye matched to your stone’s color, or preferably with crushed pieces of the same stone if available, to fill the chip, followed by polishing.

If your product has a natural, unpolished stone texture on the outside, restoration won’t be possible. If the scratch or chip is more than 2 cm deep, repair will not be successful. This should not happen.

C. Incorrectly Made Drain Holes

To date, we have encountered several different situations where someone supplied their clients with a bathtub or sink with an improperly made drain hole – one of the product’s most essential functions. The following issues are commonly encountered:

• The drain hole is finished with adhesive mortar or concrete.
  We have encountered four such cases where customers sought technical support from us. Such a bathtub is unsuitable for installation, let alone for comfortable use. The bonded part is rough and constantly absorbs water, which is detrimental to the stone. This flaw cannot be repaired, and the stone bathtub is essentially unusable. Water will inevitably seep under the bathtub, leading to flooding or water damage. Do not install such a bathtub. In the case of a sink, seepage will cause moisture to accumulate under the sink, which may rot the countertop if it isn’t made of stone.
  
  
  
  
• The drain is not the lowest point in the bathtub.
  In this case, water pools in front of the drain instead of flowing away on its own, requiring evaporation or wiping. While this may be a minor inconvenience, larger defects will be more frustrating. Additionally, this spot will be more noticeable against the body during a bath, which should be relaxing rather than a source of irritation.
  
  
  
  
• No recess for a drain box at the bottom of the bathtub.
  In many cases, the bathtub cannot be installed. This issue is often undetectable at the factory due to the product’s weight. To connect the seals and the entire drainage installation properly (remember, your bathtub is heavy, and you cannot lift it alone), you must set up a drain system correctly, which is impossible if there is no recess at the bottom for the drain box in bathtubs without overflow. This trap holds some water to prevent odors from the plumbing, forming an essential part of every standard drain assembly worldwide. However, few importers consider this critical element.
  
  
  
  
• Thickness of the bathtub bottom.
  The bottom cannot be too thin, as the rock’s monolithic nature, at such a size, contains stresses; however, it also cannot be too thick, as it prevents the installation of a standard-size drain pipe. The bottom must also maintain even thickness along the entire length of the bathtub to withstand the weight of the water and the users. Proportion needs to be maintained, or a drain box opening (as mentioned above) must be fitted to connect the drain installation, which always consists of two parts – upper and lower.
  
  
  

If you receive a bathtub with an overly thick bottom and cannot find a drain installation kit because the components are too short, try locating a disassemblable click-clack drain kit. This kit can be unscrewed into smaller components, one of which includes an internally threaded tube connecting the drain plug at the top with the trap beneath the bathtub. You can replace this tube with any other longer one, available everywhere, and any metalworker can create an internal thread, allowing you to assemble the components. Although this may sound complex, it’s straightforward except for the work required to customize the tube length, and it is consistently successful. You can share this idea with a plumber if you’re not one—they will certainly be able to handle it once they learn of this method.

• Incorrect drain hole diameter.
  Different regions of the world use varying drain standards – European drains differ from American ones, which differ from Australian ones. Receiving a bathtub with an incompatible drain hole size may prevent its connection to the sewage system if the hole is either too large or too small. While it may seem feasible to use adapters for reducing or increasing the diameter, this isn’t an option for bathtubs. So far, no solution has been found for such cases; if one becomes available, we will inform you. It’s also, of course, impossible to reduce the drain hole diameter – some have tried with cement or adhesive mortar, but as described in the first point of this section, this method doesn’t work. Additionally, enlarging the drain hole in a stone bathtub or sink is impossible as the hole is already present, and drilling it out isn’t an option.
  
  
  

  
  
  

D. Installation Problems with Stone Baths or Sinks

Certain issues may only become apparent during the attempt to install the bathtub in its final location. Some of these problems can be resolved, while others disqualify the product entirely, rendering it unusable. Common problems include:

• Uneven external bottom or base of the bath tub.
  If the level difference is below 2 centimeters, the bathtub is well-leveled and can be installed almost anywhere. However, if the slope or base level difference exceeds 5 centimeters, installation is impossible as water won’t flow toward the drain. Such a bathtub becomes useless because mechanical leveling of the bathtub bottom to achieve proper drainage or base correction is impossible, as it would compromise the thickness and safety of the bottom. This poses a risk of cracking due to stress or vibrations when filled with water, potentially causing significant damage where installed.
• Improper polishing of stone sinks and bathtubs.
  Instead of polishing the interior (a labor-intensive process), some products are covered with a transparent lacquer (a type of paint that mimics high polishing) or filled with wax. New, unused products may appear to be properly finished, but with weeks of use, the lacquer will inevitably start peeling off in flakes like old paint, leaving a rough surface that absorbs water and retains dirt. This will increase the bathtub or sink’s weight up to twice as much and may lead to soaking. Over time, this can result in the stone cracking completely.

You can restore the finish with proper polishing, but it requires either taking the product to a local stone workshop, which is challenging for a bathtub, or using professional stone polishing tools, which are expensive. Unfortunately, dishonest manufacturers frequently use these methods, knowing they save time at the cost of durability, but also aware that the product will be far from their factory when the issue arises.

• Poorly finished interior.
  A poorly polished interior in a marble bathtub may pose a risk of scratches to users. An uneven surface does not enhance comfort, and covering it with glue or adhesive mortar won’t resolve the issue, as the bathtub will continue to absorb water over time. 
  
  

E. Harmful Stone Chemicals

The substances used to polish or finish stone bath tubs or sinks cannot, unfortunately, be verified by the buyer. This can only be judged based on the general quality standards implemented in the manufacturing company. Therefore, when it comes to the health impact, such products should only be purchased from verified sources or companies that can showcase their products in reputable hotels, resorts, or spas that had to verify these products before purchasing.

Some manufacturers also possess additional certifications and have their products tested by government-run, independent institutes that issue certificates confirming the safety of these products and ensuring they contain no harmful substances.

F. Natural Causes in Stone

There are situations that no manufacturer, regardless of experience, can foresee. This is because we work with products created by nature. No one can predict what we will find inside a stone block after carving 5, 10, or 30 centimeters, or how petrified wood will behave in your specific climate conditions. Although it’s fossilized, it remains an organic material that “works” – these are exceptionally rare products but can react unusually in various environmental conditions, such as differing humidity and climates.

When it comes to petrified wood, which developed from ancient trees millions of years ago beneath the earth’s surface, taking responsibility for it is challenging because our lifespans are too short compared to the time it took to form. We work with materials created by nature, not artificially mixed compounds with known proportions. This is what defines the beauty of nature and makes these products unique.

You Are No Longer a Novice – You Now Have Extensive Knowledge About Natural Stone

Now you possess significant knowledge about natural stone used in the production of granite, onyx, and marble sinks, as well as free-standing stone bathtubs for homes, gardens, spas, and hotels. Use this knowledge to evaluate your purchase from other sources, or reach out to us and tell us what you need. At Lux4home™, you will receive products made according to our expertise and standards, meeting your expectations while securing a direct-from-manufacturer price. The choice is yours.

If you encounter a case with a purchased bathtub or sink that isn’t covered here, feel free to contact us, share photos, and we’ll do our best to help resolve your issue.

If You Have Experienced or Heard That Even a Personal Visit to Indonesia Doesn’t Guarantee the Quality You Expect
Perhaps the products delivered to you during transport weren’t what you personally selected in Indonesia—don’t hold it against the sellers there. Please consider that cultural differences, business approaches, and life experiences play a role. While certain practices may be unacceptable and surprising in many countries, they can be seen as natural elsewhere. At Lux4home™, we understand this, which is why we registered our company in the EU to provide full accountability under international trade regulations, where quality and legal standards regarding product liability are stringent.

While we respect Indonesian culture, what is obvious to us and to you may look completely different from an Indonesian perspective. This is one reason why many customers choose our services—we deliver exclusively European quality. Some made this decision after initially trying to work with other “cheap” suppliers.”

If These Qualities Matter to You in These Products:

• Safety of Use – Products that do not meet safety standards may lose their functionality and pose a real health hazard, such as by releasing harmful substances into the water.
• Product Durability – Lux4home™ products are a long-term investment. Properly selected, protected, and crafted natural stone will last for decades, making it a more cost-effective solution.
• Convenience – Stone bathtubs and sinks are not just decorative items—they are meant for daily use for many years. Choosing a well-crafted product provides both durability and convenience. Lux4home™ bathtubs are designed for easy maintenance without the risk of leaks, discoloration, or cracks.
• Long-Term Savings – By compromising on quality today, you risk paying twice—first for a cheap product and later for its replacement or repair. Lux4home™ offers quality that minimizes the risk of additional costs in the future.
• Trust – Lux4home™ products are chosen by renowned clients, such as luxury hotels, resorts, and spas, who understand that their guests expect the highest quality and comfort. We don’t just manufacture stone products; we create long-lasting furnishings that will remain in excellent condition for years, even with the heavy use typical of hotel spas.
• Respect – Lux4home™ shows exceptional respect for each client, as you are someone special who doesn’t look for standard solutions, like an acrylic bathtub. If your vision has already led you here, you deserve recognition. You deserve a product that will last, not a compromise for a lower price. You deserve the real thing, not an imitation of your dreams.”

Work with us!