The strike comes after wage negotiations in the industry deadlocked.
The General Industries Workers Union of SA (Giwusa) said on Thursday that their members as well as those from Solidarity, the SA Chemical Workers' Union and the Chemical, Energy, Paper, Printing, Wood and Allied Workers' Union were demanding increases and improvements because "workers' wages and living standards have stagnated."
Giwusa said companies that would be affected by the strike were Consol Glass, Nampak Glass, PFG Glass, PG Glass, and Owens Corning, among others.
The employers were offering a 5% increase from July 1 and another 0.5% from January 1 next year.
Workers' demands include a wage increase of 8%, six months fully paid maternity leave, a 40-hour working week without loss of pay, and compassionate leave of five days per occasion.
"Last year's increase was not enough because this increase was taken away by high food prices and increased transport costs.
Giwusa said: "More importantly, workers are also, paying much more for basic services like electricity, water and sanitation. There is no free education for children and workers have now to pay high school fees."
Croukamp said: "It has also come to Solidarity's attention that the management of Consol Glass is intimidating workers in an attempt to discourage them from taking part in the strike.
"Workers are also being offered bribes, in the form of double overtime pay, if they do not go on strike," the union alleged.
Croukamp said these actions by employers were illegal and there were numerous Labour Court judgements confirming that it was illegal to intimidate workers or to offer workers compensation for refusing to strike.
"I should like to assure workers that this strike conforms to all legal requirements and that workers enjoy the protection of the law.
"To strike is a right that has been granted to us in terms of legislation."