A three-step cleaning methodology to remove the yellowing of the Carrara marble in Oslo Opera House

Transcription

1 A three-step cleaning methodology to remove the yellowing of the Carrara marble in Oslo Opera House Prof. Pagona-Noni Maravelaki School of Architecture, Laboratory of Materials for Cultural Heritage & Modern Building MaCHMoB Scientific collaboration: Prof. Lucia Toniolo Politecnico di Milano Dr. Ioannis Arabatzis NanoPhos SA 1

2 THE OSLO OPERA HOUSE CONDITION ANALYSIS AND PROPOSAL FOR CLEANING, PROTECTION AND MAINTENANCE OF EXTERIOR MARBLE Prof. N. Maravelaki 2

3 The problem: identification of the deterioration phenomena Aims: - to gain a deep insight into the causes of the discolouration (chromatic alteration). - to assess the conservation condition of Carrara marble, with particular regard to the severe environmental conditions. - to provide solutions for the removal of yellowing Prof. N. Maravelaki 3

4 Macroscopic images Microscopic images Prof. N. Maravelaki 4

5 Summary of the results by PoliMi (Responsible: Prof. Lucia Toniolo) 1. Inorganic oxidized iron compounds (Fe3+), which sometimes are known for being implicated in the staining of marble, were not detected on the surface: Fe is not associated to the surface yellowing 2. The degradation of Faceal Oleo HD and PSS 20 could be responsible of the yellowing phenomenon, having different intensities according to the morphological features of the surfaces and the environmental specific outdoor condition. Microscopic image of the surface of a tile FTIR spectrum of extract with hexane from the yellow powder Prof. N. Maravelaki 5

6 Phase 1. Condition report and identification of the deterioration phenomena Summary of the results by PoliMi: 3. The deteriorated by-products were detected even some mm under the surface and the yellowing can be observed up to about 20 mm from the surface, due to their diffusion during the drying process Prof. N. Maravelaki 6

7 Assessment of Various Cleaning Agents Prof. N. Maravelaki 7

8 Categories of cleaning agents A. Pure solvents SLV B. Liquid solutions SLT Chemical characterization i. Ethyl Acetate (EA) ii. Propylene glycol (PG) iii. 1-chloropentane (1-ChlP) iv. p-xylene (pxln), v. NitroDiluted (ND) (commercial mixture of isomers of xylene, n-butyl acetate, methyl isobutyl ketone and 1-Methoxy-2-propanol) vi. Hexane (HXN) vii. Dimethyl Sulfoxide (DMSO) i. Mixture of various organic solvents (F17b and F25) ii. Mixture of organic solvents along with an amphiphilic anionic surfactant (F27) C. Agar i. Organic solvent (F5) ii. Oxidant Agent (F6) Application Immersion for a maximum of 3 days Immersion for 18h (F25/F27) or direct application using Japanese paper (F17b) Direct application on the surface D. Photocatalytic agents PA E. Nanogels of Microemulsions (ME) NGME F. Nanogels of advanced Micelles (MC) Solutions NGMS i. TiO 2 colloidal solutions (F10 and F13) ii. UV irradiation i. Amphiphilic-based colloidal systems of microemulsion (oil-in water) (F4a, F7, F9, F12, F16, F17a, F19, F20 and F24) ii. Amphiphilic-based colloidal systems of microemulsion (oil-in water) in the presence of chelating agents (F4b and F4c) i. Conventional and advanced amphiphilic-based micellar solutions (F15, F18, F21, F22 and F23) Direct application and subjection to UV Direct application on the surface or on Japanese paper Direct application on the surface or on Japanese paper Prof. N. Maravelaki 8

9 Assessment of Various Cleaning Agents P1 P2 P3A P3B P6 Cleaning Agent (44 Designed Agents and 7 Pure Solvents) F11a, F23, F28, F29, F30, F31 EA, PG, HXN, F2a, F11a, F14, F16, F17a, F17b, F21, F24, F26, F28, F29, F30, F31, F33, F34, F35 DMSO, F2a, F11a, F14, F23, F27, F28, F29, F30, F31, F35 F11a, F28, F29, F30, F31 EA, PG, ChlP, pxln, ND, F1a, F1b, F2a, F2b, F3a, F3b, F4a, F4b, F4c, F5, F6, F7, F8, F9, F10, F11b, F12, F13, F14, F15, F16, F17a, F18, F19, F20, F21, F22, F24, F25, F26, F28, F29, F30, F32, F33, F34, F35, UV Chemical mechanism of the three key-steps of the optimum cleaning procedure 9

10 Chemical mechanism of the three key-steps of the optimum cleaning procedure C1: 2 h application C2 (with Japanese Paper): 2 h application C3: 18 h application Cleaning Results in Lab 10

11 Results of the Three-Steps Cleaning Methodology A. Colour Parameters The lower the ΔΕ* 2, the better is the cleaning Marble Sample L* a* b* % Change of b* 1 ΔΕ* 1 (stained) ΔΕ* 2 (refer.) Reference 85.2 (±1.3) -0.6 (±0.05) 0.2 (±0.06) P1 P2 P3A P3B P6 Stained 79.9 (± 1.35) 0.2 (± 0.02) 6.4 (± 0.68) After Cleaning 83.0 (± 1.12) -0.1 (±0.04) 3.0 (±0.56) Stained 77.1 (±1.2) 1.3 (±0.3) 12.4 (±1.3) After Cleaning 80.4 (±1.63) 0.4 (±0.02) 5.7 (±0.92) Stained 80.0 (±1.7) -0.4 (±0.2) 4.1 (±0.9) After Cleaning 82.8 (±1.7) -0.4 (±0.1) 1.4 (±0.09) Stained 78.5 (±1.3) 0.8 (±0.3) 8.5 (±1.2) After Cleaning 81.0 (±1.5) 0.3 (±0.1) 3.8 (±0.9) Stained 75.0 (±1.4) 1.5 (±0.4) 13.2 (±0.7) After Cleaning 80.6 (± 1.1) 0.7 (±0.28) 7.6 (±0.6) Cleaning Results in Lab 11

12 Results of the Three-Steps Cleaning Methodology B. Macroscopic images of Marble -53% of b*& ΔΕ* 1 = % of b*& ΔΕ* 1 = % of b*& ΔΕ* 1 = 3.9 Cleaning Results in Lab 12

13 B. Macroscopic images Results of the Three-Steps Cleaning Methodology -55% of b*& ΔΕ* 1 = % of b*& ΔΕ* 1 = 8.0 Cleaning Results in Lab 13

14 Results of the Three-Steps Cleaning Methodology C. Scanning Electron Microscopy images: PoliMi P2 tile The cleaned P2 surface exhibited a grain detachment and etching along with a visible boundaries decohesion, but not to a greater extent than that observed for the stained counterparts Absence of Si in the electron microscopy study Cleaning Results in Lab 14

15 P6 tile -42% of b*& ΔΕ* 1 = 8.0 P6 marble after the application of the F28 CA: (a) treated and untreated surface and (b) different water absorption capacity of the two surfaces and (c) cleaned surface with NGS and OxA but without CA (F28). Prof. N. Maravelaki 15

16 Results of the Three-Steps Cleaning Methodology D. 2D and 3D Optical microscopy images/ FTIR Spectra Optical, 3D and scanning electron microscopy coupled with EDX, colorimetric measurements and FTIR, proved that the three-step cleaning tests applied to stained samples can successfully remove the organic part responsible for the yellowing Cleaning Results in Lab 16

17 On-site Application On-Site Application August

18 On-site Application A. Colour Parameters and Comparisons Marble Sample % Change of b* 1 ΔΕ* 1 ΔΕ* 2 P1_1 Before After P1_2 Before After P1 Lab cleaning P2 Before After P2 Lab cleaning P3A Before After P3A Lab cleaning P3B Before After P3B Lab cleaning P6_1 Before P6_2 Before P6 Lab cleaning On-Site Application August 2016 P3A & P6: Directly affected by the intensive wind 18 during the first day of application

19 B. Macroscopic images of Marble On-site Application P1 P2 P3A P3B On-Site Application August

20 Conclusions and General Recommendations In terms of individual cleaning parameters the following should be carefully considered during the cleaning on-site application: 1. The thickness, the variety of the applied polymers and the different colour intensity of the polymeric coating imply that a differentiation in the application time of the C1 step cleaning should be followed. In the smooth tiles e.g. P3A and especially P6, more than 2 h are recommended as application time for obtaining the desirable C1 action. 2. The C1 and C3 cleaning step should be applied in a paste form; only in that condition a large surface area of contact between cleaning agent and yellowed surface can be achieved. Especially, the 1 st step with C1 is decisively significant, since it induces the cracking of the polymeric coating. Provided that this cannot be achieved, neither C2 nor C3 cleaning step could effectively promote any yellowing removal. This is exactly what happened in P3A and P6 pilot application and partially in P1. 3. The C2 step requires the use of a filter paper and application of 1 h. 4. The climate conditions and especially the wind velocity should be carefully considered, since they promote the solvent evaporation, thus preventing the cleaning agents action. Prof. N. Maravelaki 20

21 Conclusions and General Recommendations In terms of evaluating the overall on-site cleaning performance the following conclusions can be drawn: 1. According to the optimum cleaning results obtained in lab, our expectations for the yellowing removal cannot exceed a 65% discoloration reduction. 2. The discoloration reduction of the rough tiles P2 and P3B is equal to 48 and 51%, respectively; this achievement can be considered as effective removal of the yellowing, very closely to the lab results. Provided that rough tiles prevailed in the OOH, it can be argued that the major part of discoloration could be effectively removed by the proposed cleaning procedure. 3. The proposed mechanism of the discoloration removal is in agreement with the obtained on-site cleaning performance. The C1 cleaning step determines the cleaning efficiency and should be applied in increased time intervals according to the thickness and darkness of the polymeric coating. 4. All the above mentioned points gave important reasons for the need to employ personnel with specific skills in the Built Conservation Heritage, capable of supervising the scale-up of the cleaning procedure. In terms of general comments and recommendations: 1. The advancement of the yellowing over time will most probably follow an increasing rate. This means that the marble surfaces should be cleaned before any protective application. 2. There is a continuous interaction between marble discolored surface and environment. If the marble surface remains unclean, the yellow discoloration will be expanded. 3. Cleaning should be followed by protection 21

22 Prof. N. Maravelaki 22

23 Thank you for your attention Scientific Responsible: Prof. Pagona-Noni Maravelaki Researcher: Dr Chrysi Kapridaki Scientific collaboration: Prof. Lucia Toniolo Politecnico di Milano Dr. Ioannis Arabatzis NanoPhos SA 23