1、從外觀上判斷

1. Judging from appearance

通過外觀上觀察和手感可初步判斷石膏粉質量的優劣。外觀上看，白度高的石膏粉細度目數高，質量好，價格較高；而發灰發黑、里面有黑色雜質的石膏粉質量較差。用手的拇指和食指搓捻石膏粉，手感發沙粗糙的 石膏粉細度糙，質量較差、價格較低；而手感細膩的石音 粉說明細度細，質量較好，價格也會較高。

By observing the appearance and feeling, the quality of gypsum powder can be preliminarily judged. Visually, gypsum powder with high whiteness has high fineness, good quality, and high price; Gypsum powder that turns gray and black, with black impurities inside, has poor quality. Rubbing and twisting gypsum powder with the thumb and index finger of the hand, the texture of the gypsum powder is coarse and sandy, with poor quality and low price; And the delicate texture of Shiyin powder indicates fine fineness, good quality, and higher price.

2、測定結晶水含量

2. Determination of crystal water content

石膏粉是一種結晶混合物，其中會含有生石膏、半水 石膏和無水石膏(過燒石膏）。在炒制過程中欠火夾生會出現生石膏，或者火大、炒制時間過長造成過燒會出現無水石膏，這些都會影響石膏的凝結時間，影響生產的正常 使用。有時由于石膏粉放置時間過長受潮，也會影響正常 使用。根據經驗和資料介紹，通過測定結晶水的含量，可判斷石膏粉質量的好壞。

Gypsum powder is a crystalline mixture that contains raw gypsum, hemihydrate gypsum, and anhydrous gypsum (calcined gypsum). During the frying process, if there is insufficient heat, gypsum may appear, or if the heat is too high or the frying time is too long, anhydrous gypsum may appear, which can affect the setting time of gypsum and affect the normal use of production. Sometimes, prolonged exposure to moisture can also affect normal use of gypsum powder. Based on experience and information, the quality of gypsum powder can be determined by measuring the content of crystalline water.

3、測定石膏粉的凝結時間

3. Determining the setting time of gypsum powder

凝結時間包括初凝時間和終凝時間。石膏粉凝結時間的質量標準是：在標準稠度下，一般初凝時間不小于 6min,終凝時間不大于25min。適宜的凝結時間是石膏粉 在生產中正常使用的先決和必要的條件。初凝時間過短或終凝時間過長都不合適。

The setting time includes the initial setting time and the final setting time. The quality standards for the setting time of gypsum powder are: under standard consistency, the initial setting time is generally not less than 6 minutes, and the final setting time is not more than 25 minutes. The appropriate setting time is a prerequisite and necessary condition for the normal use of gypsum powder in production. Short initial setting time or long final setting time are not suitable.

4、測定試餅直徑

4. Measure the diameter of the test cake

按生產中石膏和水的比例，可通過觀察和測量試餅的直徑大小（流動性）,來判斷石膏粉質量的優劣和決定 其在生產中能否使用。試餅直徑的大小與水量、膏水比例 以及石膏粉的質量等因素有關。

According to the ratio of gypsum and water in production, the quality of gypsum powder can be judged and its suitability for use in production can be determined by observing and measuring the diameter (fluidity) of the test cake. The size of the trial cake diameter is related to factors such as water volume, gypsum water ratio, and the quality of gypsum powder.

5、生產中試注

5. Production trial injection

按生產中石膏和水的比例，確保所采用的器具、操作 人員、設備和工藝方法一致，選擇一個小型胎型母模進行 生產模型的試注，與生產中正常使用的合格石膏粉的模型澆注過程進行對比。若待測石裔粉凝結時間正常合理、 操作順利不注桶，則說明該石膏粉是合格的石膏粉；若待 測石膏粉凝結時間非正常，凝結時間太短注桶，或者凝結 時間太長甚至不凝固，這樣的石膏粉不合格，生產中絕對不能使用。

According to the ratio of gypsum and water in production, ensure that the instruments, operators, equipment, and process methods used are consistent. Select a small tire mold for trial injection of the production model, and compare it with the pouring process of qualified gypsum powder used normally in production. If the setting time of the tested stone powder is normal and reasonable, and the operation is smooth without pouring into the barrel, it indicates that the gypsum powder is qualified; If the setting time of the tested gypsum powder is abnormal, the setting time is too short to pour into the bucket, or the setting time is too long or even does not set, such gypsum powder is unqualified and cannot be used in production.