褪色壁畫之科學影像檢測記錄案例探討──以臺南大甲慈濟宮三十六官將壁畫為例

A Case Study of Photographic Recording of Faded Wall Paintings - Former 36 Guan-Jiang Mural of Tzu-Chi Temple in Dajia, Tainan City

攝影記錄為文化資產保存科學調查的基本工作項目，可透過不同的攝影成像技術應用，協助彩繪壁畫保存現狀、顏料種類與技術工法等視覺化分析，因而被廣泛應用於文史調查、保存修復與管理維護等工作。但對於圖稿褪色、佚失之彩繪壁畫，通常除使用可見光加以記錄外，一般不會再做進一步檢測。本文以嚴重褪色的彩繪壁畫為對象，運用基本的科技影像檢測方法，嘗試呈現目視已無法辨識的圖稿內容。本文以臺南大甲慈濟宮修建時切割保留之三十六官將壁畫虎邊壁堵為案例，該壁堵的彩繪圖稿已嚴重褪色至只剩淡紅、綠色塊，幾乎未留存任何可供辨識之圖紋。作者運用近紅外線及紫外線螢光檢測方法進行成像，經檢測結果顯示，過去常用於探測彩繪隱蔽底稿的紅外線影像檢測方法，在本案例中，並未能呈現目視以外的其它圖紋；反之，常用於檢測彩繪表面保護層狀況之紫外線螢光影像，卻能呈現殘存於壁體內無法被肉眼辨識的圖稿原跡。期透過本文之實務經驗，能提供彩繪壁畫調查研究者進行褪色壁畫調查作業時之參考。

Photographic records are a basic undertaking in the scientific preservation of cultural assets. The application of different photographic imaging technologies can assist in the visual analysis of the condition of wall paintings, the types of paints used and application methods, etc. As a result, they are widely used in preservation and restoration. However, for faded and lost wall paintings, except for the use of visible light to record, generally no further testing will be done. This article focusses on these faded and missing wall paintings and uses basic image detection methods to try to obtain the content of the artwork that can no longer be recognized visually. It takes as an example the 36 Guan-Jiang mural at Tzu-Chi Temple in Dajia, Tainan City. The color image on the wall has faded to a reddish green block, and there is hardly any recognizable picture. The author used near-infrared and ultraviolet fluorescent imaging. The results show that infrared imaging did not show any patterns that were not visible in normal images. The ultraviolet fluorescent image used to assess the condition of the protective layer on the painted surface did show some details of the original artwork that cannot be recognized by the naked eye. Through the practical experience gained in this case, it is hoped to provide a reference for the future survey of the faded wall paintings.