Many students don't understand the difference between gouache and acrylic before learning Xi colors, so I will explain it to you in detail and have a full understanding of these two pigments before learning Xi.
Acrylic and gouache differ in a number of ways.
Differences in materials and properties
Acrylic pigment is a water-soluble pigment, which forms a porous film after drying, becomes water-resistant, brightly colored, the color can be overlapped, the pigment layer is soft, the adhesion is strong, and the preservation is strong. This pigment is bright, pure, and has a bright surface luster. Its painting materials are not limited, and can be painted on canvas, ordinary paper, glass, stone, walls, clothes, cloth and other materials. However, unidirectional glass has a smooth surface and does not adhere well to acrylic pigments. In addition, acrylic paintings can be modified repeatedly and repeatedly. In the process of painting, if the paint is not very thick, the picture can basically dry in ten minutes. When the acrylic paint dries, it is very strong and insoluble in water, just like plastic.
Gouache paint, on the other hand, is a painting made of water and powder pigments. It is characterized by being between opaque and translucent, and can be painted in heavy colors and thick paintings, or translucent thin paintings like watercolors, and the colors can produce gorgeous, soft, and bright artistic effects. Generally, gouache is painted on gouache paper, and the gouache paint is still soluble in water after drying, which is obviously different from acrylic.
The difference in picture effects and techniques
Acrylic painting and gouache painting are also very different in painting techniques, because acrylic does not dissolve in water after drying, so acrylic paint can be painted with layered dyeing techniques, and the effect of painting is very layered, and it can be painted very realistically. The gouache paint dissolves in water, and it cannot paint a very realistic picture, and it is generally a style with more obvious brushstrokes, and you can also paint the feeling of watercolor. In addition, acrylic can not only be painted in a realistic style, but also can be painted with a thick brushstroke, which is a material that artists are very fond of nowadays. Gouache is used more by students in the examination stage. 
Differences in color saturation
Gouache pigments and acrylic paints have different color saturations, what saturation?It is the brightness of the color, the color saturation of acrylic is higher than that of gouache, the acrylic paint is more vivid, and the gouache is doped with more powder, so the saturation is low, and the painted painting is also more powdery, while the acrylic painting is brighter.
The above is the difference between propylene and gouache, I hope it will be helpful to everyone.