How to identify the quality of gypsum powder?

1、测定结晶水含量

1. Determination of crystal water content

石膏粉是一种结晶混合物，其中会含有生石膏、半水石膏和无水石膏(过烧石膏）。在炒制过程中欠火夹生会出现生石膏,或者火大、炒制时间过长造成过烧会出现无水石膏，这些都会影响石膏的凝结时间,影响生产的正常使用。有时由于石膏粉放置时间过长受潮,也会影响正常使用。根据经验和资料介绍,通过测定结晶水的含量，可判断石膏粉质量的好坏。一般合格的石膏粉结晶水的含量在4.5~5.5之间^若石膏粉的结晶水含量远低于此标准值,则说明石膏粉过烧,注模时凝结时间太长甚至不凝固;若石膏粉的结晶水含量远高于此标准值，则说明石膏粉欠火或者受潮,注模时凝结时间短。以上两种情况的石膏粉都不合格,在生产中不能使用。

Gypsum powder is a crystalline mixture containing raw gypsum, hemihydrate gypsum and anhydrous gypsum (overburned gypsum). In the process of frying, raw gypsum will appear when it is under fired, or anhydrous gypsum will appear when it is over fired due to high fire and too long frying time, which will affect the setting time of gypsum and the normal use of production. Sometimes the normal use will also be affected due to the moisture of gypsum powder due to too long storage time. According to the experience and data introduction, it can be judged by measuring the content of crystal water The quality of broken gypsum powder is good or bad. Generally, the content of qualified gypsum powder crystal water is between 4.5 ~ 5.5 ^ if the content of gypsum powder crystal water is far lower than this standard value, it indicates that the gypsum powder is over burned and the setting time is too long or even does not set during injection molding; if the content of gypsum powder crystal water is far higher than this standard value, it indicates that the gypsum powder is under fire or damp and the setting time is short during injection molding. The above two cases are different Gypsum powder is unqualified and cannot be used in production.

检测石膏粉结晶水含量的方法是：准确称取4(TC烘干后冷却至室温的试样质量G(—般为2?5g),放置于恒重的铂金坩埚（或瓷坩埚）中，准确称取其质量为G1;在230±5°C下灼烧2h，取出移人干燥器内，冷却至室温后称取其质量为G2，则其结晶水百分含量为(Gt—G2)/GX100。

The method to detect the crystal water content of gypsum powder is as follows: accurately weigh the mass g of the sample cooled to room temperature after drying 4 (TC) (generally 2? 5g), place it in a platinum crucible (or porcelain crucible) with constant weight, and accurately weigh its mass as G1; burn it at 230 ± 5 ° C for 2h, take it out and transfer it into a dryer, cool it to room temperature, and weigh its mass as G2, then the percentage content of crystal water is (gt-g2) / gx100.

2、测定石膏粉的凝结时间

2. Determination of setting time of gypsum powder

凝结时间包括初凝时间和终凝时间。石膏粉凝结时间的质量标准是：在标准稠度下，一般初凝时间不小于6min,终凝时间不大于25min。适宜的凝结时间是石膏粉在生产中正常使用的先决和必要的条件。初凝时间过短或终凝时间过长都不合适。如果在使用中初凝时间太短，小于6min,则证明石膏粉没有炒熟夹生，或受潮内部含有生石裔，影响注模操作,表现为生产中注桶，耽误生产;若终凝时间太长，远大于25tnin,则说明石膏在炒制时过烧，里面含有过烧石膏，表现为注模时易漏浆,甚至石膏浆不凝固，影响生产。

The setting time includes the initial setting time and the final setting time. The quality standard of the setting time of gypsum powder is: under the standard consistency, the initial setting time is generally not less than 6min and the final setting time is not more than 25min. The appropriate setting time is the prerequisite and necessary condition for the normal use of gypsum powder in production. Too short initial setting time or too long final setting time is not appropriate. If the initial setting time is too short in use If the final setting time is too long, much more than 25 tnin, it indicates that the gypsum is over burned during frying and contains over burned gypsum, which is easy to leak slurry during molding, or even the gypsum slurry does not solidify, affecting the production.

这两种情况的石膏粉在生产中都不能使用。故通过凝结时间的测定可判定石膏粉质量的优劣或者决定该石膏粉在生产中能否使用。

The gypsum powder in both cases can not be used in production. Therefore, the quality of gypsum powder can be determined by measuring the setting time, or whether the gypsum powder can be used in production.

3、从外观上判断

3. Judging from appearance

通过外观上观察和手感可初步判断石膏粉质量的优劣。观察就是看外观包装袋质量情况和石膏粉的外观颜色，手感就是用手搓一搓石膏粉的糙细程度(细度）。

The quality of gypsum powder can be preliminarily judged by appearance observation and hand feeling. Observation is to see the quality of appearance packaging bag and the appearance color of gypsum powder. Hand feeling is to rub the roughness (fineness) of gypsum powder by hand.

(1)若包装塑料编织袋的材质质量差、松软强度低、做工粗糙、编织稀疏(单位面积内的经纬数目不达标）、颜色发灰绿黑色、内部没有防潮塑料袋、出现撒料现象、三无产品或外观标识(种类名称、生产厂家、商标、重量、联系方式等）不齐全的石膏粉则很大可能不符合质量标准、档次质量差，质量稳定性也不能保证。反之，那些包装塑料编织袋用材好、做工精致、颜色发白、强度高、编织经纬密集、内部有防潮塑料袋、封口严密、外观印刷清晰、标识齐全、不撒料的石膏粉一般质量较好、档次高，质量有保证。一般使用这种包装袋的石裔粉白度高、细度细。若石膏粉是质量上乘的、高附加值的高强度石膏粉、特种石膏粉(如母模石裔粉、原模石膏粉或树脂石膏粉），其价格很高,是普通石膏粉的3?9倍。

(1) If the packaging plastic woven bag has poor material quality, low soft strength, rough workmanship, sparse weaving (the number of longitude and latitude per unit area does not meet the standard), gray green black color, no moisture-proof plastic bag inside, scattering phenomenon, and no product or appearance identification (type name, manufacturer, trademark, weight, contact information, etc.) incomplete gypsum powder may not meet the quality standards, poor grade quality, and quality stability can not be guaranteed. On the contrary, those packaging plastic woven bags have good materials, exquisite workmanship, white color, high strength, dense weaving longitude and weft, moisture-proof plastic bags inside, tight sealing, and clear appearance printing The gypsum powder with complete marks and no material spreading is generally of good quality, high grade and guaranteed quality. Generally, the stone powder in this packing bag has high whiteness and fine fineness. If the gypsum powder is high-strength gypsum powder and special gypsum powder with high quality and high added value (such as master mold stone powder, original mold gypsum powder or resin gypsum powder), its price is very high, which is 3-9 times that of ordinary gypsum powder.

(2)外观上看，白度高的石膏粉细度目数高，质量好，价格较高；而发灰发黑、里面有黑色杂质的石膏粉质量较差。用手的拇指和食指搓捻石膏粉,手感发沙粗糙的石膏粉细度糙，质量较差、价格较低；而手感细腻的石音粉说明细度细，质量较好，价格也会较高。

(2) In appearance, the gypsum powder with high whiteness has high fineness, good quality and high price; while the gypsum powder with gray and black hair and black impurities inside is of poor quality. Rubbing and twisting the gypsum powder with the thumb and index finger of the hand, the gypsum powder with rough hand feel has rough fineness, poor quality and low price; while the stone sound powder with fine hand feel shows fine fineness, good quality and high price.

本文的精彩内容由济南石膏粉提供知识提供，本网站还有很多的精彩内容，更多的内容您可以点击进入//www.gochiism.com我们有专门的客服为您解答问题

The wonderful content of this article is provided by Jinan gypsum powder. There are many wonderful contents on this website. You can click to enter more contents //www.gochiism.com We have special customer service to answer your questions