膠（にかわ）は古来より、主に木材、紙などと相性が良く、接着剤として使用されて来た。
動物・魚類の、皮・骨・腱・内臓膜などを主要原料とし、これらを石灰水に浸してから水とともに熱して、得られた抽出液を濃縮して棒状、板状に乾燥させたもので、原料の主成分はタンパク質で、簡単に言うと未精製のゼラチンである。
墨なども煤を膠で固めたもの。
兎膠・・・耐水性がある 鹿膠・・・接着力が強い 牛膠・・・三千本が代表的
この他、粒膠や軟靭膠などが挙げられます。
現代では、天然、新岩、合成、水干絵具以外にも、顔料（絵具）が増え多様化しているためなのか、アートレジンやアートグルーなどのメジューム系着剤もよく見かけるようになった。
膠絵（ Glue painting ) と言うくらいに、日本画は膠とは切っても切れない繋がりをもち、その関係は何百年単位で遡る。
顔料（絵具）を、どんな接着剤で定着させるかが重要だと考えがちだが、日本画にとって重要なのは明礬ドーサと膠の組み合わせが重要だと私は考えている。
自分の体質にあった、自分の技法にあった膠（接着剤）を見つけられることが、自分の絵画世界を広げる大きな一歩に繋がることだと思う。
Since ancient times, glue has been used as an adhesive mainly because of its compatibility with wood and paper.
The main ingredients are the skin, bones, tendons, and viscera of animals and fish, which are soaked in lime water, heated with water, and the resulting extract is concentrated and dried into sticks or boards.
Sumi ink, for example, is also made by solidifying soot with glue.
Rabbit glue: water-resistant Deer glue: strong adhesive strength Cow glue: Sanzen glue is typical
In addition, grain glue and soft glue are also listed.
In addition to natural, new-rock, synthetic, and water-dried paints, today, medium-type adhesives such as art resin and art glue are also commonly found, perhaps because pigments (paints) have increased in number and diversity.
Japanese-style painting is inseparably linked to glue, so much so that it is called glue painting, and the relationship goes back hundreds of years.
Although we tend to think that it is important what kind of glue is used to fix the pigments (paints), I believe that the combination of alum dosa and glue is the most important factor in Japanese painting.
I believe that finding a glue (adhesive) that suits one's constitution and one's technique is a big step toward expanding one's painting world.