The document discusses the properties, classification, and manufacturing processes of gypsum products, particularly focusing on the dehydration of gypsum to produce calcium sulfate hemihydrate. It details methods for measuring setting time, including loss of gloss, penetration, and indentation tests. The document also outlines different types of gypsum products and their applications in various contexts.

1. GYPSUM PRODUCTS
PART - 1
Dr.shiva

2. Introduction

3. History

4. Why its called as plaster of paris?
• Montematre - place in
paris where the large
scale of plaster is
manufactured

5. GYPSUMTHAT
AVAILABLE IN
NATURAL / RAW
FORM

6. • Hydrated
• dehydrated
• Rehydrated
• Dehydrate but little amount of water

7. CALCIUM SULFATE DIHYDRATE

8. MANUFACTURINGOF GYPSUM

9. Gypsum after manufacturing (powder form)

12. • Hydrated(dihydrate) • Dehydrated(hemihydrate) • Rehydrated • Dihydrate(dehydration)

13. How does different material like dental
stone and dental plaster….. are formed??

14. • With out water
• With water and by closing it with lid
• With some stuff and closing it with lid
• With some other stuff and closing it with lid

15. On heating
α – hemihydrate(closed kettle)
iii -110–120°C – water+ autoclave
iv - 30% calcium chloride solution
+ autoclave
iv/v - 130°C – (sodium succinate)
autoclave
β- hemihydrate(open kettle)
i & ii -110–120°C with out water

16. Open kettle Closed kettle

17. GYPSUM PRODUCTS – ADA 25
•Gypsum products are the results of partial dehydration
of gypsum, which produces calcium sulfate hemihydrate
(CaSO4.1/2 H2O).

18. CLASSIFICATION OF GYPSUM PRODUCTS

21. GYPSUM PRODUCTS
Calcium sulfate β –hemihydrate
Type I
Type ii
Calcium sulfate α-hemihydrate
Type iii
Type iv
Type v

31. Measurement of SettingTime
•1. Loss of glossy test or glass disappearance.
•2. Penetration test.
•3. Indentation test.
•4. Exothermic reaction.

32. Loss of glossy test or glass disappearance.
As the reaction proceeds
some of the excess water
is taken up in forming
dihydrate by capillary
action so that the mix
loses its gloss.
When loss of glass occurs
further manipulation of
gypsum mass should be
avoided

33. Difference between indentation and penetration

34. Vicat penetrometer

35. •The rod is lowered until it contacts the surface of the material
and then the needle is released and allows penetrating the
mix.
• When the needle fails to penetrate to the bottom of the
container the material has reachedVicat setting time.
• Initial setting time is defined as the time from the beginning
of the mixing until theVicat needle no longer penetrates the
entire depth (5 cm) of a given mass of material.

36. Indentation test

37. Indentation test
(gillmore needle)
Small
113.4 g
1/12 inch in
diameter
Large
453.6 g
1/24 inch in
diameter

40. MIND MAPPING

41. Gypsum products
ADA specification
number
Manufacturing
Open
Close
properties
Mixing time
Setting time
Working time
Final set
Initial set
Measuring of
setting time
Vicat
Gillmore needle
Los of gloss
Exothermic heat
Setting reaction Classification Uses of gypsum

42. Thank you
Drshivasai