科學分析優化文物修護之研究—以呂鐵州「後庭」膠彩畫為例

《後庭》（1931，原名《蜀葵與雞》）是日治時期膠彩畫家呂鐵州（1899–1942）之代表作。該作呈現當時台灣畫家受西方寫實主義影響的寫生繪畫風格，並大量使用日本傳統「盛上技法」繪製而成。這種利用顏料逐層堆高成半浮雕的效果，乃膠彩繪畫中極具高難度的技法，因而使該作更顯彌足珍貴。《後庭》大約在20年前曾經修護，但修護後卻發現盛上技法區域的顏料層仍嚴重龜裂，亟需再次進行整體修護以便妥適保存。面對獨具時代背景卻又嚴重受損的珍貴作品，若未先理解劣化的根源，便無法提出適當的修護保存策略。對承接修護的單位而言，能否自評為具有受理該案修護的適格能力與對作品的風險評估上確實是一大挑戰。因此，為建立嚴謹的評估模式，本研究首開國內先例，在受理修護前先進行相關科學分析與試驗評估，獲得關鍵結論後再正式受理修護委託。本研究首先以「加固材料分析委託案」針對關鍵材料進行分析試驗，包括：(一)開發將展色劑與顏料分離之樣本前處理技術；(二)運用顯微紅外線光譜法（Micro-FTIR）結合元素分析儀串聯同位素比值質譜法（EA-IRMS），判定《後庭》的顏料展色劑較接近西方繪畫使用的阿拉伯膠；(三)以創新模擬劣化試驗方法，探討顏料龜裂與展色劑相關性，並擬定出最適化修護措施。正式受理委託修護後，採行非破壞性科學檢測以釐清作品材質特徵和先前修護痕跡。首先運用一般光源攝影確立前次修護有更改裝裱形式，以及顏料錯位與補彩溢塗等情形；背面光、透光與紫外線螢光攝影則顯示呂鐵州利用不同材質紙張拼貼畫面，使作品基材紙張厚薄不均，且畫心紙材已隨龜裂現象一併拉撐斷裂；透過紅外線攝影（860nm）與X光螢光分析儀（XRF）推測作品顏料成分，則規範出清潔與加固溶劑使用限制。綜合前述分析試驗和非破壞檢測結果，制定了修護策略是必須先提供穩定的基底材與裝裱支撐，再針對顏料層進行加固並填補缺失，使畫面回歸原創性與穩定性。實際進行作品解體，將背面的五層背紙層層揭除之後，發現兩個因前人修護不當而產生的嚴重人為二次傷害：(一)前次修護師採用中式裝裱常用的短纖維宣紙，加上漿糊黏著力不足，以至於產生裝裱紙張空鼓、無法給予作品足夠支撐而促使基底材隨著顏料層一同斷裂的狀況；(二)因早期修護無科學檢測的輔助，導致修護師誤判紙層而產生揭薄基底材紙層使作品厚薄不一之情形更加劇烈。因此在歸納上述結果後說明顏料層的龜裂原因，其實是包含作品本身材料老化與結構層複雜加上後人不當修護等相互影響所致。本研究執行之修護乃根據作品實際需求訂製規劃各項材料與技法，不僅將作品基底材裂開的縫隙良好銜接、給予強韌且具保護力的支持體，更將模擬試驗結果結合油畫修護校正顏料層變形的技術，將錯位的顏料層復位。最後基於倡導「文物修護美學」的理念，重拾在台灣幾乎瀕臨失傳的日式裝裱技術，重現《後庭》原日式屏風裝裱風貌，解決畫面中心銜接處畫意不接的情形，更彰顯原有美感與歷史時代特徵。綜此，本研究建立起一套以解決問題為導向的現代科學優化文物修護保存模式，特別是針對重要文物的安全性，透過修護前的調查分析與試驗，將科學分析所掌握的事實證據基礎與修護技術經驗緊密結合，依此擬定較適化的修護保存策略與執行方案，提供文物修護實務與保存科學領域參考。

關鍵字

文物保存修護；呂鐵州；膠彩；保存科學；屏風

並列摘要

Backyard (1931, originally titled Hollyhock and Chicken) is the masterpiece of Lu Tieh-chou, an Eastern Gouache artist from Japanese Colonial Period in Taiwan. The painting is representative of the Western-influenced realistic-style painting of contemporary Taiwanese artists at that time and employs extensive use of the traditional Japanese painting technique, moriage. This technique in which multiple layers of paint are built up to produce a realistic and relief-like surface is difficult to carry out in Eastern Gouache paintings, which makes this painting especially precious. Backyard had undergone conservation treatment twenty years ago, but it was discovered that the moriage on Backyard suffered from serious cracks afterwards and was in urgent need of another conservation treatment for long-term preservation. Considering the unique historic significance and severe damages on this precious work of art, it is impossible to propose an appropriate preservation strategy without a thorough understanding the origin of the damage. For the conservation team, determining whether they hare capable to carry out the treatment and assess the amount of risk that would bring to the work of art was a big challenge. Therefore, to establish a rigorous assessment process, this study began with scientific analysis and experimentation prior to conservation treatment — the first methodology without precedint in Taiwan — and after the key conclusions were formulate, the conservation treatment project was approved to execute. This reserch started with the “Analytical Study of Pigments Layer Consolidation” project focusing on analytical testings of key consolidants including: (1) developing the sample preparation technique separating binder and pigment; (2) using Micro-FTIR in combination with EA-IRMS to determine the binder used in Backyard which has the characteristic closer to gum arabic used in Western watercolors; (3) using a simulation experiment investigate the correlation between paint cracking and binder, and developing an appropriate treatment proposal. After this project was officially commissioned, non-destructive analysis was employed to explicate physical characteristics and traces of previous conservation treatment. First, normal light photography was used to confirm that the previous treatment had changed the mounting style and to identify areas of overpaint; transmitted light and UV-induced visible fluorescence photography revealed that Lu Tieh-chou joined different types of paper together to form the painting's primary support, causing it to be uneven in thickness and resulting in cracks and tears on this primary support. IR (860 nm) imaging and XRF analysis were used to identify pigments that aids the choice of solvents and consolidants used for treatment. Based on the results of the scientific and non-destructive analysis, a conservation methodology was developed. This included firstly providing a stable base layer and mounting support, and secondly consolidating and reinforcing cracks on the paint layer so that the painting could return to its original appearance and stable form. During treatment, the removal of five layers of backing paper from the back of the painting revealed two major damages caused by improper previous treatment: (1) the combination of using Chinese short-fibered xuan paper and weak paste resulted in delaminated pockets in the mounting papers that did not sufficiently support the artwork and caused the primary support to separate from the paint layer; (2)due to the lack of aids by scientific testing, the previous conservators misjudged the paper layers resulting in skinning of the primary support which caused the unevenness of the paper thickness to be even more severe. In summary, the cause of cracking on the paint layer is due to the interaction of aging of the original paint layer, the structural complexity of the artwork's layers, and inappropriate conservation treatments. The materials and techniques of the conservation treatment of this study were customized and based upon the needs of the work of art. The goals were not only to better joint the cracks on the primary support and to provide a strength and protective support, but also combine simulation experiment results with oil painting conservation techniques for moderating the deformations of paint layer and to return misaligned paint layers. Finally, in accordance with "aesthetics of cultural heritage conservation" and recapturing the nearly lost techniques and arts of Japanese-style mounting in Taiwan, the treatment of Backyard revealed its original Japanese folding screen format, resolved the issue of misalignment at the center of the painting, and highlighted its original beauty and historic characteristics. To summarize, this study established a set of scientifically optimized cultural heritage conservation models that were problem solving-oriented particularly for the safety of cultural objects. Throught the Pre-treatment investigation, analysis and testing, and the combination of the foundation of factual evidence obtained through scientific analysis, and technical conservation skills, and appropriate conservation proposal could be formulated. This study provides a novel conservation methodology for future conservation practice and preservation science.