Conservation Case Study • Research Archive
Tropical Model: 2-Year Observation CasePost-treatment monitoring in real tropical conditions
Published: March 2026•Location: Puchong, Selangor•Keywords: Tropical Model, Oil Painting, Observation Study
Last Data Update: June2026 (Month 2/ Year 1) | Next Scheduled Inspection: July 2026
Technical and safety information for Paraloid B-72 and Laropal A81 were consulted from the manufacturer's documentation provided by CTS – Conservazione Tessile Sistemi and BASF/Kremer.
Project Investigator
Tony Ng Chit Keong
Independent Oil Painting Conservator, Malaysia
Role: Malaysia conservator responsible for treatment, monitoring design, ATP testing, environmental logging, and long-term documentation.
1. Project Abstract
This case documents a two-year observational study following the full application of the MTC (Multi-Layer Tropical Conservation) Model on a contemporary oil painting. The treatment strictly follows the MTC structure, including the application of an isolation layer (Paraloid B-72) and a sacrificial layer (Laropal A81), without the introduction of any retouching layer, as no visual reintegration was required. Following treatment, the artwork was returned to its original, uncontrolled tropical environment. No artificial climate stabilization was introduced. The purpose of this study is not to produce definitive conclusions, but to document material behaviour, environmental interaction, and system stability over time under real-world conditions. All observations should be understood as conditional and subject to revision based on long-term monitoring.
2. Project Timeline & Status
Month 0Completed
Baseline treatment, varnish application & documentation
April 2026
Month 1 (Y1-M1)Completed
First monthly inspection & ATP swabbing
May 2026
Month 2 (Y1-M2)Completed
Monthly inspection & ATP swabbing
June 2026
Month 3 (Y1-M3)Pending
Routine monthly environmental monitoring
July 2026
Month 4 (Y1-M4)Upcoming
Routine monthly environmental monitoring
August 2026
3. Background
Oil paintings in tropical environments are continuously exposed to high humidity, temperature fluctuation, and airborne particulate matter.
In such conditions, long-term stability is influenced not only by biological factors, but also by material interaction, moisture exchange, and layer behaviour over time.
Rather than focusing on reactive restoration, this project adopts a structured, preventive approach through the MTC Model, which introduces defined material layers to manage interaction between the original paint surface and the surrounding environment.
This case does not aim to eliminate environmental influence, but to observe how a controlled material system behaves within it.
4. MTC Model Statement
The MTC (Multi-Layer Tropical Conservation) Model is a structured conservation approach developed in response to the conditions of tropical environments, where humidity, temperature fluctuation, and material instability are persistent factors.
Rather than relying on a single treatment layer, the model introduces a controlled multi-layer system consisting of an isolation layer and a sacrificial layer, while preserving the original paint structure.
The purpose of this model is not to eliminate environmental influence, but to manage interaction between materials over time. It is designed to allow maintenance, reversibility, and long-term observation under real-world conditions.
This model should be understood as an evolving framework, informed by ongoing case-based observation rather than fixed conclusions.
Full framework reference:
https://tonyngchitkeong.com/MTC_Model/Malaysia_Tropical_Conservation_Model.html
5. Potential Fungal Genera in Tropical Heritage Environments
The following fungal genera are frequently reported in tropical and high-humidity environments and are known to contribute to the biodeterioration of organic cultural heritage materials such as oil paintings, canvas supports, paper, and varnish layers. These genera are included here as a reference framework for potential microbial risks in tropical climates (Sterflinger 2010).
| Genus | Typical Substrate | Potential Risk to Oil Paintings |
|---|---|---|
| Aspergillus | organic binders, canvas | pigment staining and surface colonization |
| Penicillium | varnish layers, canvas | discoloration and spore spread |
| Cladosporium | humid surfaces | surface colonization |
| Alternaria | organic materials | pigment alteration and staining |
Table 1 — Fungal genera commonly associated with biodeterioration of cultural heritage materials in humid climates (after Sterflinger 2010).
6. Conservation Objective
• To implement the MTC Model as a structured, multi-layer conservation system
• To establish a stable isolation layer using Paraloid B-72
• To introduce a sacrificial layer (Laropal A81) as a controlled interface for future maintenance
• To document system behaviour under uncontrolled tropical conditions
• To generate observational data for long-term evaluation and future refinement
7. Experimental Methodology & Rationale
This project is not designed as a controlled experiment, but as a long-term observational study based on real collection conditions.
Methodological Structure (MTC Model):
• Original structure (support and paint layer) – left unchanged
• Isolation layer – Paraloid B-72
• Retouching layer – not applied
• Sacrificial layer – Laropal A81
This layered system separates intervention materials from the original surface while allowing future maintenance and reversibility.
Environmental Context:
After treatment, the artwork was returned to its original location without environmental control. This includes natural fluctuations in humidity, temperature, and airborne exposure typical of tropical indoor conditions.
Monitoring Approach:
• Environmental readings
• ATP surface testing
• Visual inspection
• Surface condition tracking
Rationale:
The purpose is to document behaviour over time rather than confirm a predefined outcome. All findings are considered provisional and subject to change.
8. Methodological Disclaimer
This project represents an observational monitoring study conducted under real collection conditions. Unlike laboratory-based conservation experiments, environmental variables such as humidity, temperature, and airborne biological exposure were not artificially controlled.
The data presented therefore reflect the natural environmental fluctuations typical of tropical climates and are intended to provide practical insights into preventive conservation strategies under real-world conditions.
8. Environmental Description
The painting is displayed within a naturally ventilated residential environment without air-conditioning. It is positioned on a wall facing the main entrance, where routine opening and closing of the door may contribute to minor fluctuations in temperature and relative humidity. The household also contains a domestic cat, which may increase the presence of airborne dust, fur, and particulate matter within the surrounding environment.
9. Study Limitations
This study represents a single-object monitoring project conducted under real-world collection conditions rather than a controlled laboratory environment. Environmental variables such as humidity and airborne biological exposure were not experimentally regulated. The observations presented therefore represent case-specific monitoring data rather than generalized experimental conclusions.
9. Data Logger Preliminary Calibration Test
Prior to deployment, a preliminary 7-day side-by-side observation was conducted to compare general trend consistency between the two devices. Minor short-term deviations were observed during periods of rapid environmental fluctuation, such as air movement caused by door opening or fan activation. However, both devices demonstrated closely aligned long-term temperature and relative humidity trends under relatively stable environmental conditions.
10. Treatment Overview
The full assessment, detection, and judgment processes leading to this treatment are extensively documented in case study TPA281-2026-005.
Following that assessment, the conservation treatment was carried out according to the MTC Model:
Surface Preparation
Mechanical cleaning and localized solvent action were performed to reduce surface contaminants prior to layer application.
Isolation Layer
Paraloid B-72 was applied as a stable, reversible isolation layer separating the original paint surface from subsequent materials.
Sacrificial Layer
Laropal A81 was introduced as a removable protective layer designed to receive environmental impact and allow future maintenance without affecting the original surface.
No retouching layer was applied, as visual reintegration was not required.
12. Research Significance
This case study provides empirical baseline data for adopting proactive preventive conservation in Southeast Asian environments, rather than waiting for bio-deterioration to occur. The successful utilization of Paraloid B-72, coupled with passive microclimate framing, offers a low-maintenance, cost-effective, and highly protective standard operating procedure for the preservation of modern oil paintings in challenging tropical climates. This protocol significantly reduces the future need for invasive restorative cleaning, thereby preserving the original integrity of the artist's work from day one.
13. Decision Log
Observation Period: Y1-M0Status: Initial baseline observation
Trigger ObservationArtwork reinstalled in original display location.
Regional ambient humidity (Selangor, Puchong) recorded at approximately 75%, while indoor environmental RH at the artwork location measured at 80.6%, with temperature at 29.8°C.
A surface reading taken at the backing board recorded approximately 65.8%.
ATP surface reading recorded at 0 RLU.
InterpretationInitial baseline data indicates elevated indoor humidity conditions (80.6% RH), exceeding the regional ambient reference.
A lower moisture response is observed at the backing board surface (65.8%) compared to the surrounding environment, suggesting a difference between environmental RH and material response at this stage.
ATP readings do not indicate detectable microbial activity.
No internal microclimate data is available at this point.
This dataset serves as a reference snapshot for subsequent observations.
DecisionNo intervention at this stage.
RationaleThis initial dataset establishes a baseline under relatively high humidity conditions.
Given the limited scope of data at this stage, no assessment of internal environmental behavior or system performance can be made.
Continued observation is required.
Risk ConsiderationElevated indoor humidity (80.6% RH) may present a potential long-term risk if sustained.
Current data does not indicate immediate risk, but environmental trends remain to be evaluated over time.
Action TakenBaseline data recorded. Routine monitoring initiated.
Observation Period: Y1-M1Status: CONTINUED BASELINE OBSERVATION
Trigger ObservationRoutine monthly observation conducted following baseline recording period.
Visual examination, UV inspection, close-up photography, and ATP surface testing revealed no significant observable changes compared to the previous observation cycle.
/Minor particulate accumulation and isolated foreign debris were observed under magnification and were gently removed using a soft brush without further intervention.
/An additional ATP reading was conducted along the painting edge area, producing a surface reading of 876 RLU.
/A temperature and relative humidity data logger was installed adjacent to the artwork to initiate long-term environmental monitoring.
InterpretationCurrent observations do not indicate measurable visual or surface-level deterioration when compared with the previous baseline documentation.
ATP readings from the painting edge cannot currently be interpreted conclusively due to the absence of prior comparative data from the same location.
The elevated edge reading may reflect either pre-existing localized surface activity or recent environmental accumulation; therefore, no definitive assessment regarding microbial progression can be made at this stage.
Environmental monitoring has now been expanded through the introduction of continuous temperature and relative humidity logging to support future longitudinal interpretation.
DecisionNo interventive treatment recommended at this stage. Continued observation advised.
RationaleCurrent findings remain visually and materially stable within the scope of available comparative documentation.
Due to the limited temporal dataset and absence of progressive deterioration indicators, continued observation is considered more appropriate than immediate interventive action.
Risk ConsiderationElevated ATP activity detected at the painting edge may warrant continued attention during subsequent observation cycles.
However, without prior reference data or confirmed visual correlation, the present reading should not be interpreted as definitive evidence of active microbial development.
Environmental humidity conditions remain relatively elevated and may contribute to long-term biological or material risk if sustained over extended periods.
Action TakenSurface particulates removed using a soft brush under magnified observation. Environmental monitoring initiated through installation of a temperature and relative humidity data logger adjacent to the artwork. Baseline environmental recording protocol established for future comparative analysis.
Observation Period: Y1-M2Status: STABLE CONDITIONS OBSERVED
Trigger ObservationRoutine monthly observation conducted under the established monitoring protocol. Visual examination, UV inspection, and close-up photography revealed no measurable changes compared with the previous observation cycle. No surface deposits, biological growth, coating alterations, or structural concerns were identified during examination. ATP surface testing returned a reading of 0 RLU, while ATP testing conducted at the previously monitored painting edge location produced a reading of 353 RLU. Compared with the previous edge reading of 876 RLU, the result indicates a reduction in detectable biological activity at the monitored site. No cleaning, stabilization, or other conservation interventions were undertaken during this observation period.
InterpretationCurrent observations indicate continued visual and material stability. The absence of detectable ATP activity on the painted surface and the reduction in ATP readings at the monitored edge location suggest that biological activity remains low and has not progressed since the previous observation cycle. As testing was conducted at the same edge location used previously, the lower ATP reading provides a more meaningful comparative reference than earlier baseline measurements. No evidence currently suggests active microbial development or material deterioration.
DecisionNo interventive treatment recommended. Continue routine observation and environmental monitoring.
RationaleThe artwork remains stable based on visual examination, UV assessment, photographic documentation, and ATP monitoring results. The reduction in edge ATP readings compared with the previous cycle does not indicate increasing biological risk and is consistent with a stable environmental condition. In the absence of deterioration indicators or adverse environmental trends, continued observation remains the most appropriate conservation strategy.
Risk ConsiderationAlthough ATP activity at the monitored edge remains detectable, the observed reduction from previous readings suggests a lower level of biological activity at the tested location. Environmental monitoring recorded a temporary increase in ambient relative humidity to 80.3% RH on 15 June 2026, exceeding the preferred range for long-term preventive conservation. However, no corresponding visual changes, biological growth, coating alteration, or material instability were observed during the current inspection cycle. Continued environmental monitoring and periodic ATP testing remain advisable to determine whether elevated humidity events become recurrent or result in measurable long-term effects. No immediate biological or material risk is presently indicated.
Action TakenNo conservation treatment or cleaning intervention was performed during this observation period. Visual examination, UV inspection, close-up photography, ATP testing, and environmental data review were completed in accordance with the established monitoring protocol. Monitoring records were updated for longitudinal comparison.
16. Visual Documentation
Baseline Imaging (Pre-treatment)
Post-Treatment Imaging
Monitoring Comparison
Visible Light / Macro (Microscope)
Visible Light / Close-Up
UV Fluorescence
17. Environmental Data Graphs
Microclimate vs. Ambient Humidity Over Time
ATP Microbial Activity Index (RLU)
ATP Edge Spot Test (RLU)
Monitoring peripheral contamination risk at edge over time.
18. Quantitative Data Archive
| Observation Period | Temp (°C) | Ambient RH (%) | Inner RH (%) | Wall Moist (%) | Lux | ATP (RLU) |
|---|---|---|---|---|---|---|
| Y1-M0 | 29.8 | 80.6 | 3.7 | 223 | 0 | |
| Y1-M1 | 31.1 | 68.8 | 68.3 | 3.0 | 269 | 0 |
| Y1-M2 | 31 | 72.9 | 69.2 | 3.0 | 252 | 0 |
19. External Weather Conditions (Google Weather)
Note: The following external meteorological data were recorded on the specific day of monthly inspection to contextualize potential environmental stresses. Source: Google Weather.
| Observation Period | Ext. Temp (°C) | Precip. Prob. (%) | Ext. RH (%) | Wind (km/h) |
|---|---|---|---|---|
| Y1-M0 | 27 | 59 | 75 | 5 |
| Y1-M1 | 35 | 69 | 56 | 8 |
| Y1-M2 | 31 | 40 | 72 | 6 |
20. Observation Notes
| Observation Period | Visual Inspection | Varnish Integrity | Initials |
|---|---|---|---|
| Y1-M0 | No visible mold. Canvas tension stable. | Excellent , no blushing. | T.N. |
| Y1-M1 | No visible mold. Canvas tension stable. | Excellent , no blushing. | T.N. |
| Y1-M2 | No visible mold. Canvas tension stable. | Excellent , no blushing. | T.N. |
21. High-Frequency Logger Tracking (Combined Comparison)
Continuous automated logger data mapping fine-grained environmental interactions over extended periods.
22. Independent Microclimate Logger Tracking (Node 2)
Continuous automated logger data from secondary internal microclimate node.
References
1. Koob, S. P. (1986). The Use of Paraloid B-72 as an Adhesive. Studies in Conservation.
2. Learner, T. (2004). Analysis of Modern Paints. Getty Conservation Institute.
3. Sterflinger, K. (2010). Fungi and the Deterioration of Cultural Heritage.
4. Unković, N. et al. (2015). ATP Bioluminescence Method for Microbial Screening on Cultural Heritage.
Suggested Citation
Ng, Tony Chit Keong. 2026. Tropical Model: 2-Year Observation Case. Post-treatment monitoring in real tropical conditions. Conservation Research Archive.