14）考古金属資料の安定化処理および修復金属器の救出
被災した文化施設からは、鉄および非鉄金属を素材とする様々な金属器が救出されました。岩手県陸前高田市立博物館からは毛抜形蕨手刀（No.3）（陸前高田市小友町岩井沢検出：陸前高田市指定文化財）（図1）をはじめとする鉄器、陸前高田市小友町常膳寺の鰐口（岩手県指定文化財）（図8）、さし鍋（陸前高田市竹駒軍見洞遺跡出土）（図9）をはじめとする銅合金資料が救出され、岩手県立博物館（以下、岩手県博）に搬送されました。
陸前高田市立博物館には小友町岩井沢出土蕨手刀の他に、２振りの蕨手刀が収蔵・展示されていて、東北地方太平洋沖地震発生時には３振りとも１階の展示室で公開されていました。巨大地震発生後、襲来した大津波によって全て流出し行方不明となりましたが、関係者の懸命な救出活動によって、2011年5月6日に３振りとも１階収蔵庫内に堆積する土砂の中から発見され（図2・3）、その後岩手県博に搬送されました（赤沼2012a、赤沼・熊谷2013）。岩手県博に搬入後ただちに、肉眼による状態観察およびX線透過写真撮影が行われました。救出した３振りの蕨手刀は今から約15年前に岩手県博で保存処理が施された資料です。その折に撮影されたX線写真と救出後に撮影された写真を比較したところ、毛抜形蕨手刀の柄の一部が欠失した点を除き、顕著な劣化の進行は認められませんでした（図4）。約15年前に実施した保存処理によって、海水損による錆化の進行が抑制されたものと思われます。
鰐口（図8）には多量の土砂が混入していたものの、被災前とほぼ変わらない状態で救出されました。一方、さし鍋（図9）は救出活動終盤、陸前高田市立博物館周辺の土砂の中からようやく、破片の状態で発見されました。

14) Stabilization and Restoration of Archaeological Metal
Objects

observed except for a partial loss of the handle of a kenukigatawarabiteto sword (Fig. 4). It is assumed that preservation
treatment performed on the swords around 15 years ago
had helped suppress the progression of corrosion caused byseawater damage.
Hardly any changes were observed in the condition of thesalvaged waniguchi gong (Fig. 8) in comparison to its predisaster condition, except for the large amounts of dirt and sandcovering it. On the other hand, the pot with a spout (Fig. 9) was
found only towards the end of the salvage activities in a broken
state consisting of several pieces. They were discovered in alarge pile of dirt that had been removed from the interior of theRTCM which was being dried to sift out small artifacts.

Salvage of metal objects
Various metal items made from iron and nonferrous metals
were salvaged from disaster-damaged cultural facilities.
The following objects were salvaged from the RTCM andtransferred to the IPMM: ironware including the kenukigatawarabiteto sword (No.3) (discovered in Iwaisawa, Otomocho, Rikuzentakata City, designated as a Rikuzentakata City
cultural property) (Fig. 1) and copper alloy objects including
the Buddhist ritual gong (waniguchi ) of the Jyozenji Temple
in Otomo-cho, Rikuzentakata City (designated as an Iwate
Prefecture cultural property) (Fig. 8) and a pot with a spout(excavated from the Takekomagunmibora Site, Rikuzentakata
City) (Fig. 9).
In addition to the warabiteto sword discovered in Iwaisawa,Otomo-cho, the collection of the RTCM includes two otherwarabiteto swords. All three swords had been displayed in thefirst floor exhibition room of the museum when the Great East
Japan Earthquake occurred. The swords were washed away by
the subsequent tsunami caused by the earthquake. However,due to the concentrated effort put forth during the salvage
activities by the involved staff, all three swords were foundon May 6, 2011 in the dirt that had collected inside the firstfloor repository (Figs. 2 and 3). The swords were subsequently
transferred to the IPMM (Akanuma 2012a, Akanuma andKumagai 2013). At the IPMM, the condition of the swords wasvisually observed, recorded and X-ray transmission imaging
was performed on them immediately. Preservation treatment forthe three salvaged warabiteto swords had also been performedat the IPMM approximately 15 years ago. When the X-ray
photographs taken at that time were compared to the ones taken
after the swords were salvaged, no significant deterioration was142

鉄資料の安定化処理および修復処理する鉄器の外観を写真撮影しました。次にＸ線透過写真撮影し、資料内部の劣化状況を確認した後、表面に固着する土砂や錆を、竹串やワイヤーブラシを使って除去しました。震災前から劣化が進んでいた鉄器にはいたるところに亀裂や空隙がみられ、空隙内部にまで土砂が入り込んでいました。これらの土砂は、エアーブラシを使って可能な限り取り除きました。
錆化が進み、資料表面に黄褐色を呈する液体が吹き出ていた資料については錆層を採取し、塩素（Cl）やりん（P）といった劣化促進につながる有害元素について、EPMA分析しました。震災前に保存処理が施された蕨手刀をはじめとする鉄資料については、ドラフトチャンバー内でアセトンに浸漬し、劣化した樹脂を除去した後、精製水に浸漬し、脱塩を施しました（図5）。
脱塩はポリプロピレン製または塩ビ製コンテナで行い、脱塩液に溶出する塩化物イオン濃度が水道水以下（6ppm以下）になるまで、定期的に脱塩液を交換しながら少な
くとも10日間続けました。
脱塩処理が終わった資料を超音波洗浄機で洗浄し、減Stabilization and restoration of iron objects
The external appearance of the iron objects to be treated
was photographed. Then, X-ray transmission imaging wasperformed to assess their internal degradation. Subsequently,
the dirt and sand particles affixed to the surface of the object,
and the rust formed on the surface was removed using bamboo
skewers and wire brushes. Cracks and voids were observed
all over the archeological objects, in which degradation had
already been progressing prior to the disaster. Dirt and sandhad filled in those gaps. Such dirt and sand was removed to themaximum extent possible using an air brush.
As for the iron objects in which rust progression had caused ayellowish-brown liquid to spout from the surface, samples werecollected from the layer of rust. Then, harmful elements which
promote degradation, such as chlorine (Cl) and phosphorus (P)were analyzed by an electron probe micro-analyzer (EPMA).
Iron objects such as the warabiteto swords which had been
given preservation treatment prior to being damaged by thedisaster were immersed in acetone inside a draft chamber toremove degraded resin. Then, the items were desalinated by

第4章

№1

№2

№3

救出された蕨手刀
Salvaged warabiteto swords
図1 岩手県陸前高田市立博物館から救出された蕨手刀
Fig. 1 Warabiteto swords salvaged from the Rikuzentakata City Museum

図2 被災した陸前高田市立博物館１階収蔵庫
Fig. 2 Disaster-damaged first floor repository of
the Rikuzentakata City Museum

図4 被災前後に撮影されたレントゲン写真
Fig. 4 X-ray images taken before and after the disaster (Upperimage: before the disaster. Lower image: after the disaster)

図6 ハンドドリルによる錆の除去
Fig. 6 Removing rust using a hand drill

安定化処理と修理

修復後の蕨手刀
Post-restoration warabitetoswords

図3 蕨手刀の発見
Fig. 3 Warabiteto sword at the time of its recovery

図5 鉄器の脱塩
Fig. 5 Desalination of ironware

図7 エポキシパテによる欠損部の復元
Fig. 7 Restoration of defective parts using apaste epoxy143圧乾燥しました。資料表面に生成した錆をエアーブラシやハンドドリル（図6）、ワイヤーブラシを使って可能な限り取り除きました。表面をエチルアルコールで洗浄した後、30mass%のパラロイドNAD10アクリル樹脂を含むナフサ懸濁液を減圧含浸しました。樹脂含浸は2回以上繰り返しました。毛抜形蕨手刀のように大きく破損した鉄器のうち、実測図が現存する資料についてはそれを基にエポキシパテで欠失部を復元した後（図7）、岩絵の具を用いて古色仕上げしました。
銅資料の安定化処理および修復
鰐口およびさし鍋についても表面に固着する土砂を除去し、ギ酸を使って新たに発生した錆を可能な限り取り除きました。次に精製水で脱塩（図10）、エチルアルコールで脱水、ベンゾトリアゾール処理した後（図11）、鉄器同様30mass%のパラロイドNAD10アクリル樹脂を含むナフサ懸濁液を減圧含浸しました。
既述のとおり、さし鍋は大破し、著しく変形した破片の状態で救出されたため、安定化処理に移る前に微小試料片を摘出しEPMA分析しました。その結果、1mass%程度の塩素（Cl）が検出され、合わせて銅（Cu）、ヒ素（As）、錫（Sn）の合金を素材とすることがわかりました。
硬い地金で、それぞれの破片を不織布で包み整形を要

immersing then in purified water (Fig. 5).
The desalination was performed using containers made frompolypropylene or polyvinyl chloride. The process was repeated
while periodically changing the desalination liquid until theconcentration of the eluted chloride ions in the liquid reacheda value equal to or lower than the chloride ion concentration in
tap water (6 ppm or less). Approximately 10 days were required
to complete the desalination process.
The desalinated objects were washed using an ultrasoniccleaner, then were dried using low pressure. The rust collecting
on the material surface was removed to the maximum extent
possible using an air brush, a hand drill and/or a wire brush(Fig. 6). After cleaning the material surface with ethyl alcohol,a naphtha suspension containing 30mass% Palaroid NAD10
acrylic resin was introduced into the object by decompression
method. Resin introduction was repeated two or more times.
Among the considerably damaged iron objects including thekenukigata-warabiteto sword, those with existing surveyed
drawings were treated by restoring the areas of loss based on
the drawing using a paste epoxy (Fig. 7), and then giving anantique finish using natural mineral pigments.
Stabilization and restoration of copper objects
Dirt and sand fixed on the surface of the waniguchi gong andthe pot with a spout were removed in the manner previously
described, and the newly accumulated rust was removed
as much as possible using formic acid. Then, the objects
were desalinated using purified water (Fig. 10), dehydratedusing ethyl alcohol, and treated with benzotriazole (Fig. 11).
Subsequently, as with the iron objects, a naphtha suspension
containing 30mass% Palaroid NAD10 acrylic resin was infused
into the object by decompression method.
As described earlier, since the pot with a spout had beenbroken and was recovered in a state of many separate pieces,the minute pieces were extracted and analyzed by EPMA prior
to performing the stabilization. As a result, approximately 1
mass% Cl was detected. The analysis also revealed that the144する部位にアルミの板を添え、その上から少しずつ力を加え整形しました。岩手県博で保管されていた実測図を基に整形した破片をつなぎ合わせ、ほぼ被災前の状態に復元しました（図12）。
新たな発見
被災鉄器再生の過程で行われた金属考古学的調査によって、３種類の鋼が３振りの蕨手刀の製作に使用されていたことが判明しました。東北地方北部はもとより、関東および北海道でもほぼ同じ組成の鋼を素材とする鉄器が確認されています。8 ～ 9世紀に東日本において、海を渡る鉄の物質文化交流が展開されていた可能性が高いことを示唆する結果です。このように被災資料の再生は、被災した地域が歴史の上で果たした役割を再検討する重要な機会を我々に与えています。
大きく破損した資料を被災前の状態に再生できたのは、常日頃から機関連携による学術調査が行われ、重要な学術情報が複数の機関において保管されていたことに依拠します。今後もこれまでの取組を続けることによって、数多くの金属器を再生させることができると思われます。
赤沼英男（岩手県立博物館）

body of the pot with a spout was made from an alloy of copper(Cu), arsenic (As) and tin (Sn).
Each piece made from this hard alloy was wrapped in a
nonwoven cloth, and an aluminum sheet was placed next tothe piece to be formed. Then, force was added gradually toshape the pieces into the correct form according to the surveyed
drawing that had been kept at the IPMM. Shaped pieces werejoined together, and then the joined areas were formed again.
After completing all the treatments, the pot with a spout was
restored to a state almost identical to that of its pre-disasterstate (Fig. 12).
New discoveries
The archaeometallurgical analysis conducted on the disasterdamaged iron objects revealed that three types of steel wereused to manufacture the three warabiteto swords. Ironware
items made of steel with compositions almost identical toeither one of these three types have been found not only in the
Northern Tohoku region but also in the Kanto region and inHokkaido.
This suggests that it is highly likely that cultural exchangeof iron products had occurred in Eastern Japan in the 8th and9th centuries. The task of stabilizing and restoring disasterdamaged objects has provided us a significant opportunity to reevaluate the historical role the disaster-damaged regions haveplayed in Japan’s and Asia’s history.
It was possible to restore heavily damaged objects back totheir pre-disaster state mainly because of the scientific researchthat had been collaboratively conducted by relevant institutions
during non-crisis times, and the fact that important scientific
data had been stored at a number of institutions. It is possible tostabilize and restore many other metal cultural assets by using
the methods described in this research.

Hideo Akanuma (Iwate Prefectural Museum)

第4章

救出後
Post-salvage

安定化処理と修理安定化処理後救出後
Post-stabilization treatment

図8 陸前高田市立博物館から救出された鰐口
Fig. 8 Waniguchi gong salvaged from Rikuzentakata City Museum

大破したさし鍋
Pieces of the shattered pot with a spout

修復されたさし鍋
Restored pot with a spout

図9 修復前後のさし鍋
Fig. 9 Stabilization and restoration of a salvaged pot with a spout

図10 さし鍋の脱塩（水浸漬）Fig. 10 Desalinating the pot with a spout(by soaking it in water)

図11 ベンゾトリアゾール処理
Fig. 11 Treatment using benzotriazole

図12 破片の整形・接合
Fig. 12 Shaping and joining of the broken pieces

145