METHOD OF MAKING A RED-GLASS VESSEL

Abstract

In order to provide a method which can produce red glass vessels and which is attended by low cost in respect of the raw materials/starting materials and also in respect of control of process parameters, an appropriate method for producing red glass vessels is proposed in which a colourless molten glass composition containing at most 3% by mass of tin oxide and at most 3% by mass of copper oxide is produced, where the resultant colourless molten glass composition is refined under neutral conditions with sodium sulphate and/or calcium sulphate and with a carbon-containing reducing agent with a molar carbon/sulphate ratio of from 0.5 to 5, where glass vessels are moulded from said refined glass composition, and where the glass vessels are cooled to a temperature of below 520 degrees C. to 580 degrees C.

Claims

1. A method of making a red-glass container, the method comprising the steps of: making a colorless molten glass composition containing at most 3% by mass of tin oxide and at most 3% by mass of copper oxide; refining the colorless molten glass composition under neutral conditions with sodium sulphate or calcium sulphate and with a carbon-containing reducing agent with a molar carbon/sulphate ratio of from 0.5 to 5; molding a glass container from the glass composition refined under neutral conditions; and cooling the glass container to a temperature of below 520 C. to 580 C.

2. The method according to claim 1, wherein activated carbon is used as carbon-containing reducing agent.

3. The method according to claim 1, wherein the colorless molten glass composition is made with a content of tin oxide of from 0.2 to 3% by mass and with a content of copper oxide of from 0.06 to 3% by mass.

4. The method according to claim 3, wherein the colorless molten glass composition is made with a content of tin oxide of from 0.5 to 1.5% by mass and with a content of copper oxide of from 0.1 to 0.35% by mass.

5. The method according to claim 1, wherein the colorless molten glass composition is refined under neutral conditions with sodium sulphate or calcium sulphate and with activated carbon with a molar carbon/sulphate ratio of from 0.5 to 2.

6. The method according to claim 1, further comprising the step of: heat-treating the glass container cooled below a temperature of from 520 C. to 580 C. at approximately 620 C.

7. The method according to claim 1, further comprising the step of: making the colorless molten glass composition di-calcium phosphate or tri-calcium phosphate.

8. The method according to claim 7, wherein the colorless molten glass composition is made with a content of phosphates of from 0.01 to 5% by mass.

9. The method according to claim 1, wherein the colorless molten glass composition is made with boric acid.

10. The method according to claim 9, wherein the colorless molten glass composition is made with a content of boric acid of from 0.01 to 5% by mass.

11. The method according to claim 1 wherein the colorless molten glass composition is made with PbO or PbS pr Bi.sub.2O.sub.3 or Bi.sub.2S.sub.3.

12. The method according to claim 11, wherein the colorless molten glass compound is made with a content of PbO or PbS or Bi.sub.2O.sub.3 and/ or Bi.sub.2S.sub.3 of 0.01 to 3% by mass.

13. Use of a red-glass container made in accordance with any claim 1 as a container for foodstuffs or beverages.

Description

[0017] The invention will be explained in greater detail hereinafter on the basis of an embodiment.

[0018] A colorless molten glass compound is firstly produced from suitable raw materials and serves as starting material for the method according to the invention. Tin oxide and copper oxide are contained in the glass composition, wherein the content of tin oxide is approximately 1% by mass and the content of copper oxide is approximately 0.2% by mass.

[0019] Di-calcium phosphate and/or tri-calcium phosphate are/is also contained in the glass composition, wherein the content of di-calcium phosphate and/or tri-calcium phosphate is approximately 0.01 to 5% by mass.

[0020] Alternatively or additionally to the tri-calcium phosphate, the colorless molten glass composition can contain boric acid, wherein a range of from 0.01 to 5% by mass has proven to be particularly advantageous in view of the content of boric acid as well.

[0021] The phosphate and/or the boric acid serve/serves to modify the glass network so that the annealing or tarnishing process can be accelerated and the necessary tarnishing temperatures can be kept as low as possible.

[0022] In order to accelerate the nucleation, the colorless molten glass composition is produced with Bi2O3, more specifically with a content between 0.01 and 3% by mass.

[0023] Instead of Bi.sub.2O.sub.3, PbO and/or PbS and/or Bi.sub.2S.sub.3 can also be used for the same purpose.

[0024] What is essential in the case of the above-described materials is that they are metal compounds or heavy metal compounds that can easily precipitate out in the metallic state under the redox conditions provided in the glass melt.

[0025] The colorless molten glass composition is refined under neutral conditions with sodium sulphate and/or calcium sulphate and with activated carbon. Here, a molar carbon/sulphate ratio of approximately 1.0 is observed.

[0026] By the methods known from the prior art, glass containers are molded from the glass composition refined accordingly under neutral conditions.

[0027] Once the molding of the glass containers is complete, these are cooled to a temperature of below 520 degrees C. to 580 C.

[0028] In the described illustrated embodiment of the method according to the invention, a secondary heat treatment is performed following this cooling and is carried out at approximately 620 C. The glass containers produced accordingly are then cooled. At the end of the above-described production method, the glass containers have the desired red coloration. They are also suitable in particular for receiving foodstuffs or beverages.