The final setting is 4 hours for light plastering by hand and 70 minutes for machine spraying.

[Roy]

The final setting is 4 hours for light plastering by hand and 70 minutes for machine spraying.

The reason currently considered is that the ion temperature of the machine spraying equipment is too high (up to about 90°), the minor material additives are not resistant to high temperatures, and the loss is too significant.

 

[Cassie]

I also encountered it. The laboratory measured the setting time as 4 hours, and the machine sprayed on the wall was 1 hour. My guess is that，

1. The device was not cleaned, and the reacted dihydrate gypsum induced the accelerated reaction of hemihydrate gypsum, which shortened the setting time.

2. Stir unevenly. The spray machine only stirs for tens of seconds. The additives and powder inside are not stirred evenly, and the vitrification is not pre-absorbed, which will also affect it.

 

[Scott Kaplan]

The temperature is not convincing. Test the spread rate of the two. The glass bead breakage rate may be too high, or the mixing time of the machine spray is short, which causes the retarder didn’t fully dissolve.

 

[Luis]

The inside of your machine sprayer is not cleaned, and gypsum residues cause the coagulation time to be too fast.

 

[Chanliss]

The mixing of the machine spray is more uniform, which is probably caused by the residue of the machine.

 

[Allen]

The coagulation and hardening of gypsum is the process of dissolution and recrystallization. The high rotation speed will accelerate the dissolution rate of gypsum in water. Therefore, the coagulation time must be short.

I have primarily done experiments in this area. Under the same conditions, manual mixing, mortar mixer mixing, and mixing gun mixing have different setting times. Usually, manual mixing takes the longest time, and mixing gun time is the shortest.

In the same stirring method, the amount at one time will also affect the setting time. If you stir more, the setting time will be longer; if you stir less, the setting time will be shorter.

That's how it works for me; I need to figure out what's going on elsewhere.