1.Description
This red are strike red,before annealing it looks like clear tube but have red line inside the tube,
after annealing it turns to red.
Annealing as following:
a.Put the products into the annealing furnace.
b.Control the temperature between 515℃ and 525℃,keep for 180 mins to 220 mins, then 
drop the temperature to 400℃ then take out the products.

2.Normal size
O.D.: 4-42mm
Length:1200mm
We can also make special size for you in O.D.from 3.5 to 46mm and length less than 2500mm. 
3.Main Composition

a) SiO2: 80±0.5%

b) B2O3:13±0.2%

c) Al2O3:2.4±0.2%

d) Na2O(+K2O):4.3±0.2%

4.Physical and Chemical Properties

a) Coefficient of mean linear thermal expansion(20/300℃):3.3±0.1(10-6K-1)

b) Transformation temperature: 525±15℃

c) Melting point::1,260±20℃

d) Softening point:820±10℃

e) Density at 20℃:2.23g/cm2

f) Hydrolytic resistance at 98℃: ISO719-HGB1

g) Hydrolytic resistance at 121℃: ISO720-HGA1

h) Acid resistance class:ISO1776-1

i) Alkali resistance class:ISO695-A2