Marble in Fountains and Sebils: Restoring Stone That Lives With Water

A fountain is the structure in which stone works under the harshest conditions. Marble cladding on a wall sees rain a few times a year, while a fountain's front panel and trough get wet, dry out and get wet again every day. The Ottoman fountains and sebils in our cities have endured this cycle for centuries; the limescale crust, green algae, rust stains and worn inscriptions on them are traces of water's long relationship with stone. In this article, we explain where the deterioration in fountains comes from, which principles guide work on a historic fountain, and how to look after the marble fountains used today in gardens, hotels and residential complex entrances.

In brief: Most problems in fountain marble come from the water itself: limescale deposits, biological growth, rust from iron parts, and freezing. On a historic fountain, documentation and permits come first, followed by cleaning and repair with minimal intervention; on a modern fountain, water quality, regular draining and winter preparation are the basis of maintenance.

Stone That Lives With Water: Why Does Deterioration Progress Quickly in a Fountain?

The main mineral of marble is calcite, and calcite dissolves in water, even if only very slightly. In a fountain, water constantly flows along the same path: from the spout to the trough, and from the trough's overflow to the ground. The stone surface along this path is both slightly dissolved by the water and coated with the minerals the water carries. This is why on old fountains you see the area beneath the spout softened, the edges of the trough rounded, and the area around the overflow covered with a crust.

The wet-dry cycle brings a second problem with it. Water that enters the stone carries the salts it has dissolved to the surface, or just beneath it, as it dries. As salt crystals grow in the pores, they lift the top layer of the stone and make it flake off. In winter, the water remaining inside the stone freezes and expands; especially where there are cracks or open joints, this expansion causes pieces to break off.

The Stone Parts of an Ottoman Fountain and Sebil

Before intervening on a historic fountain, you need to know its parts, because each part deteriorates differently. In a classic Ottoman fountain, the front face where the water flows is the mirror stone (ayna taşı); the spout from which the water comes out is at its center, and the trough where the water collects lies below. There is usually an inscription on or around the mirror stone: a written panel bearing the name of the person who commissioned the fountain, its date, and often a poem. On the side faces and under the eaves there are relief ornaments, rosettes and niches.

A sebil, on the other hand, is a structure where water or sherbet was distributed free of charge to the public. It usually rises at a corner on a multi-sided plan; its faces have windows with metal grilles, and the sebil attendant would hand out water in vessels through these windows. In sebils the stone is in less direct contact with water than in fountains; however, window sills, the sockets where metal grilles are embedded in the stone, and the underside of the eaves are places where moisture and rust collect. A significant portion of the white and gray-veined marble used in many historic fountains and sebils in Anatolia comes from the quarries of Marmara Island; the coarse-crystalline structure of this stone also shows the marks of centuries of weathering very clearly.

Limescale Deposit: The White Crust on the Trough and Mirror Stone

The most common problem in fountains is limescale deposit. The calcium and magnesium in hard water settle on the stone as the water evaporates. Beneath the spout, on the inner edge of the trough and at the overflow, a yellowish or gray crust forms that can reach centimeters in thickness over time. This crust adheres firmly to the stone and often covers the reliefs or letters beneath it.

Removing limescale from marble with acid is the biggest mistake. The crust and the stone have the same chemistry, namely calcium carbonate; the acid that dissolves the crust also dissolves the marble beneath it. For this reason, on historic fountains the limescale crust is thinned with mechanical and controlled methods: with a scalpel and small hand tools, with micro-abrasive blasting, or with laser cleaning in expert hands. Even leaving part of the crust on the stone is an acceptable result; the aim is not to make the stone look new, but to preserve it. We compared the differences between these methods in our article on cleaning methods in stone restoration

Moss, Algae and Black Crust

Trough interiors that stay constantly wet and shaded side faces are suitable environments for biological growth. A layer of green algae creates slipperiness, while lichen clings to the stone surface and slowly erodes it. The stone beneath the biological layer stays damp for longer, which accelerates salt and frost damage.

City-center fountains have one more problem: black crust. On sheltered surfaces not washed by rain, under eaves and in niches, a dark, hard layer develops as a result of air pollution and gypsum formation. This crust does not just spoil the appearance; it is also a sign of deterioration of the marble beneath it. We covered how black crust forms in detail in our article on air pollution and black crust

Iron Pipes, Cramps and Spout Marks

In historic fountains, marble blocks are mostly joined to one another with iron cramps, and the cramps are fixed in their sockets with molten lead. Lead protects iron for years; but when the lead is lost or water seeps into the socket, the iron rusts. Because rust occupies far more space than the iron's original volume, it pushes the surrounding stone from within, cracks it and breaks off pieces. Most of the brown-stained cracks seen at the corners of fountains and at block joints result from this process.

Iron pipes, metal spouts and taps added later also leave marks on the stone. Iron rust forms brown and orange stains, while copper and brass parts produce greenish ones. Because these stains work into the stone's pores, they do not come out with a brush; they are drawn out over time with poultices prepared with chemicals suitable for the stone. However, the source must be addressed before stain cleaning: if the rusting cramp or pipe stays in place, the stain and crack keep progressing. In historic buildings, rusting cramps are, on an expert's decision, mostly replaced with cramps made of stainless or non-corroding material.

Inscriptions and Ornaments: Document First, Then Touch

The inscription is the identity of the fountain. The text is often worked as fine relief or incised carving; traces of paint or gilding may remain in some of the letters. Limescale, black crust or a biological layer can cover these letters and make them hard to read. Inscription cleaning is the finest and slowest-moving job on a fountain.

The basic rules followed on inscriptions and ornamented surfaces are as follows:

• Documentation first: Before cleaning, the surface is photographed in detail and the condition of the letters and ornaments is recorded with drawings or notes, so that the effect of the intervention can be monitored.
• Test area: The chosen method is first tried in a small, inconspicuous corner of the inscription, the result is examined with a magnifying glass, and the method is softened if necessary.
• Attention to paint and gilding traces: Original paint or gold traces remaining inside the letters carry valuable information; cleaning is done by working around these layers without removing them.
• No re-carving: Deepening or re-engraving faded letters alters the original text, damages the historic document and cannot be undone.

If there are broken-off pieces in relief ornaments, they are assessed separately before being put back. It is possible to complete the leaf of a missing rosette or repair a broken edge; however, the completion must be based only on a documented form and must be distinguishable on close inspection. We described techniques for completing missing pieces in our article on completing missing pieces in marble

Conservation Principles for a Historic Fountain

A significant portion of the historic fountains and sebils in Türkiye are registered cultural assets and are protected under Law No. 2863 on the Conservation of Cultural and Natural Property. On these structures, every intervention, including cleaning, requires a project approved by the relevant regional conservation council and expert supervision. Since most fountains are endowment (vakıf) works, ownership and responsibility are also often shared among municipalities or foundation institutions. If an apartment management or a neighborhood association wants to have the historic fountain in front of it cleaned, it should start by applying to the relevant institutions.

The basic principles of international conservation apply to fountains too: minimal intervention, preservation of original material, additions that are distinguishable, and methods that are reversible as far as possible. In practice, this means consolidating the fountain rather than polishing it as if newly built, removing harmful layers in a controlled way, and reducing the damage water does to the stone. We have also compiled the practices to avoid on historic surfaces in our article on historic marble surfaces

A fountain restoration on site generally proceeds in a certain order. First, the structure is surveyed and documented with photographs, and the stone types and a deterioration map are produced. Then how and where water reaches the stone is investigated: plumbing, roof and eaves, ground slope, the path of overflow water. Cleaning trials are carried out in small areas and the results compared, and the gentlest effective method is chosen. Consolidation, treatment of rusted cramps, and joint and crack repairs come after cleaning. Finally, it is decided whether the water will be turned back on, and who will carry out maintenance and at what intervals.

The most frequently skipped step in this sequence is the maintenance plan at the end of the job. If no one takes responsibility after restoration, the trough will be overgrown with algae again within a few years, the overflow will clog, and the same deterioration will start all over. For this reason, a simple maintenance schedule and the responsible institution should be clearly written into the handover.

The table below summarizes common deterioration in fountains and the right approach to each:

Maintenance of Modern Garden, Hotel and Residential Complex Fountains

Today, marble or travertine fountains are widely used in villa gardens, hotel courtyards and the entrances of residential complexes. These fountains are not historic, but they are subject to the same physics: stone that stays constantly wet collects limescale, grows algae and cracks if it freezes. In most of them the water is circulated by a pump; the fresh water added to replace what evaporates increases the mineral load a little more every day.

The basic steps of regular maintenance for modern fountains are as follows:

• Water quality: Using softened water where possible and periodically emptying and refilling the basin completely noticeably slows down limescale buildup.
• Regular brushing: If the inside of the trough and the overflow outlet are cleaned with a soft brush before the crust thickens, limescale and algae are removed before they settle into the stone.
• Stone-appropriate products: Some of the chemicals sold for pools and aquariums are acidic or chlorinated; the label of every product added to water that comes into contact with marble should be checked.
• Winter preparation: In regions where frost occurs, the fountain is drained before winter arrives, the pipes and pump are cleared of water, and the stone is covered to protect it from rain and snow.

The surroundings of the fountain are also part of maintenance. If the overflow water spreads onto the ground, the surrounding stone paving stays constantly wet, becomes slippery and produces salt efflorescence. Connecting the overflow outlet to a drain and making sure the ground slope carries water away from the fountain extends the life of both the fountain and its surroundings. In cold regions this arrangement becomes even more important, because water collecting at the base of the stone strains it a little more with every freeze.

For the maintenance of a historic fountain, we recommend first consulting the relevant authorities, and for a modern fountain, having an on-site assessment done before limescale and cracks grow. You can reach us through the service request form with a few photos of your fountain.