25.1 I am here too. Anti graffiti coating for monumental surfaces.

13/01/11

Due to the escalation of the "graffiti" phenomenon in its various forms, ranging from simple vandalism to "mural art", it is now necessary to improve measures for the protection of architectural surfaces. We are certainly required to enrich our knowledge about the materials to be protected and the products to be applied. There are different techniques for cleaning a surface from graffiti: chemical gel or solutions; steam/ high pressure water jets; micro sandblasting; and laser. Anyway, in this short article we are going to focus on the passive protection systems, in other words, polymers that does not prevent from the drawing but facilitate the removal of that: the anti-graffiti.

We are about to consider just the anti-graffiti 
sacrificial products. These products are partially or totally removed when the cleaning operations take place and, as a consequence, need to be replaced by new coatings. Due to the reversibility, they are particularly appreciated for the restoration of monuments. On the other hand, the anti-graffiti in the permanent grades are made of irreversible cross-linking resins which deposit a homogeneous and resistant layer, which does not allow the graffiti to penetrate the substrate because those are insoluble in the solvent of the protective coating.
In such a way the graffiti can be removed without damaging the anti-graffiti resin. Anyway, the irreversibility of the product is associated with an aesthetic disadvantage: the treated surfaces look glossy. This makes these irreversible products inappropriate for the facades of monumental architecture.

By using the word "graffiti" we have missed the original meaning of the term: "a decorative technique of partially scratching off a top layer of plaster or some other material to reveal a differently colored material beneath ". 
Instead, that word recalls 'writings and drawings made with sprays and markers. In some cases they use pencils, charcoals, crayons, chalk, including unusual materials such as lipsticks and nail polish. Considering the majority of graffiti are created with spray (more than 50% of urban graffiti) and markers, we should focus first on the mechanism of deposit, and intervene correctly by means of both preventive and cleaning operations.


Spray paints- 
We refer to particular paints, in which the pigment is mixed with a thermoplastic resin, conveyed by a volatile solvent (light hydrocarbons such as butane and propane- keeping in mind that CFCs have been banned).
Markers- Even here we have a pigment dispersed in a solvent, with a smaller amounts of resin compared to the paint. This makes the medium less viscous and more penetrating and the solvent is absorbed by capillarity, and the pigment with it.

In both cases, the pigments are dispersed in solvents with high volatility. When using the spray, vaporization at the outlet nozzle reduces the ability of the pigment to go deep into the porosity; on the contrary, when using the marker, penetration into the porosity of stones or plasters is fostered by the felt tip so that it is very hard to remove. Using solvents for cleaning could make it worse because they can drag the pigments deeper inside the pores and generate stains. This consideration about the level of removal is confirmed by the results of a case study: ICR [1] and ICCROM [2] studies on the effectiveness of protective coatings at the time of removal. For all the tested products, removal of spray paints from limestone or marble is satisfactory, while problems occur for the marker graffiti.

Requisites and criteria for the good choice

The anti-graffiti must comply with standard requirements for treating monumental surfaces as follow:
- Durability_ The efficacy must persist for a reasonable period of time, with minimum maintenance interventions (costs cutting)
- Resistance to aging and absence of bad interactions with the substrate
- Absence of harmful by-products that can be generated over time. This leads to exclude the products affected by microbiological attack, such as those based on polysaccharides (PSS 20 by All-Remove), or siloxanes based ones (Funcosil of Remmers) [3]

- Easy removing of graffiti (not just a theoretic reversibility)
- No changes in color
- Low toxicity and low impact on the environment
- Low cost

For the correct evaluation of a product we need to check these sources of information:
  • technical and safety data sheets for each product on the market
  • the results of tests conducted on the specific formulations
  • the results of tests conducted on the interactions between the products and different substrates and surfaces (reduction of the permeability to vapor, color changes and so on)
  • Monitoring data records collected over time

Anti graffiti CTS products:
 Art-Shield 1 
CTS, operating mainly in the field artistic monumental architectures, gained a valuable experienced and is now able to offer different formulations (Art Shield-1, introduced in this article, and fluorinated Fluoline HY and Fluoline PE, which will be considered in the next bulletins). All these types are sacrificial protective and applicable on stone with different levels of porosity, and also with different levels of aesthetic impact.

Both Art-Shield 1 and the fluorinated elastomer of Fluoline HY had already been addressed in 2004 during the case ICR / ICCROM [1][2] as suitable solution for the protection of stone surfaces. This study reports data about chromatic variation and protective capacity, on marble and limestone (travertine), before and after artificial aging.


The validity of these active ingredients has been confirmed by the very recent guidelines for the removal of disfiguring writings from architectural surfaces, enacted by the Regional Committee for the preservation of the Cultural Heritage and Landscape of Emilia Romagna, and by the 'Soprintendenza' for Archaeological Heritage and Landscape of the provinces of Bologna, Modena and Reggio Emilia, and by the 'Soprintendenza' for Archaeological Heritage of Emilia Romagna, and the City of Bologna.
The Guidelines have been formulated on the basis of a complex study that included:
  • a classification of all the types of dirtying
  • the creation of a database
  • A research conducted on various construction sites and workshops and the identification of the best substances for the removal and further protection.

The results, collected in the book "Against graphic acts of vandalism", can also be downloaded from the official website [5]. Those outcomes confirm that for the surfaces of the monuments in Bologna (sandstones, bricks, plaster), characterized by high porosity, the best results were obtained operating with a fluorinated h.m.w elastomeric copolymer in solvent. It is the active ingredient of the protective Fluoline HY, which also has the advantage of a low-impact on color. In the case of light slightly absorbent stone or wood and metals, ii is recommended to choose aqueous emulsions of paraffin based polymers, such as Art-Shield 1.

When selecting the active ingredients, CTS had ruled out the use of anti-graffiti based on siloxanes or on Si(OR)n chain structure, that excel as water repellent but act badly against solvent-based products like markers. Commercial products generally have a good color effect, but their irreversibility was also emphasized by the study carried out by the Central Institute (Imagine "0" IR 200 distributed by IRCA, BS-28 by Wacker and Guardian by Zernike; Funcosil by Remmers).

Art Shield-1 efficient barrier effect is due to the formation of a transparent film, thin and tight that covers the pores of the treated surfaces, and prevents graffiti from penetrating deeply into the substrate.

The type of wax makes the treatment with low chromatic effect and chemically stable, in contrast to products based on natural waxes, which are low effective at the time of the cleaning off the inscription and show degradation over time (B-Wax distributed by All -clean).
Similar products (PMC 20 by CIR, G-Pro by Mega Corp., Wallgard Graffiti Barrier by Mapei and AGS Grafficoat 3 by Tensid) have shown relevant color change in the ICR study mentioned above.
During a study conducted by the Government Institution for the administration of the Cultural Heritage of Rome under the scientific coordination of the Central Institute of Restoration [4] six anti-graffiti products, based on various active substances, were compared. Art Shield-1 was found to be the best protective agent for removing spray paints and marker graffiti from marble, tuff and peperino (volcanic tuff).
With regard to bricks, the product is effective only for the spray traces, maybe because the marker is deeply absorbed in the substrate of the walls: as a matter of fact no other product worked well in this specific circumstance. OFF A / 700 by Agep (another product based on paraffin) turned out to be the best product for treating travertine surfaces. 
All the other products (all of them containing fluorine) did not give acceptable results. 

The table below summarizes the results of the study:


Product                               Marble          Travertine         Tuff         Peperino          Bricks(volcanic tuff) 
OFF A/700 (Agep
)                     -                    ++/+                -                 -                           - 
Akeogard CO (Syremont)           
-                       -                   -                 -                           - 
Fluorophase 3 (Phase)               
-                       -                   -                 -                           -
Prostone (Pelicoat)                    
-                       -                   -                 -                           - 
Protectosil (Degussa)               
-                       -                    -                 -                           -
Art-Shield 1 (CTS)                    
++                     -               ++/+++         +++                     +++/- 


* spray / marker drawings

Art-Shield 1 exhibits excellent reversibility. We should mention two situations when removing the bad writings/drawings:


Surfaces Product                               
Art Shield 4 in gel ready for usebase of 
Not treated with Art-Shield 1                  
low toxicity solventsand surfactants


Treated with Art-Shield Shield 1              Hot water (over 80 ° C)
                                                            at low pressure
and if it is not feasible, just use Art-Shield 4

Art Shield-1 is the most popular anti-graffiti product used by Italian restorers. For two decades now it has been successfully applied on monuments such as Dome in Milan, the Basilica of Saint John and the Ara Pacis in Rome, and the Fountain of Neptune in Naples. Since 2003 it has been selected and applied for the protection of the most important monuments in Madrid, and in 2006 those of Bilbao and many others all round Spain.

References:
1.     Vigliano G. “
Graffiti e antigraffiti” Bollettino ICR 1, (2001).
http://iscr.beniculturali.it/index.php?option=com_content&task=view&id=14&Itemid=16 
2.     Borrelli E., Moreno Caballero B., Vigliano G.; “Progetto Axum – Sperimentazione prodotti antigraffiti” ICCROM, 2000. 
3.     Krumbein W.E. “
Graffiti and antigraffiti – An appraisal” International Workshop on conservation of Architectural Surfaces: stones and wall covering, Venice (1992). 
4.     Cardilli L., Cancelieri C., Bernardini C.; “
Graffiti e antigraffiti: sperimentazione su pietre all’aperto in contesto urbano e verifica in laboratorio”, Records from the Conference “Lo stato dell’arte 2”, Genova, September 27-29 th, 2004. 
5.     
www.emiliaromagna.beniculturali.it/index.php?it/221/linee-guida-vandalismo-grafico

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