Sunday, July 31, 2011

Drywall Staining? Tannin Bleed from Recycled Paper?

News Flash: It looks like drywall manufacturers are cutting corners... AGAIN.

The first offence took place from 2001 to 2007 when Chinese drywall manufacturers were using left over coal ash which is a waste product of coal fired power plants. They were using this as a "filler" along with gypsum, the primary ingredient in drywall, to produce sheets of drywall. After the product was installed in homes it began to off gas. The sulfur off gassing will eat away copper, metal, door knobs, etc. and may be causing adverse health side effects. There is a website chinesedrywall.com were one could find more about it and to see if you qualify for a class action lawsuit or some sort of retribution should your house have been constructed with Chinese Drywall.

Example of Tannin Bleed
Today the current problem with drywall is "Drywall Staining". The problems of producing toxic drywall is in the past. Now it is just an issue of aesthetics. This is a fairly new issue for the construction industry specifics have not been nailed down yet. It is thought that the staining is caused from one of two souces: tannin bleed from the recycled paper facing or high alkaline sizing compound used in the manufacturing process.
The problem appears when latex paints soak into the drywall and the acids or tannin rises to the surface. The staining does not occur as much if the drywall is cured or the paint is drying a a well ventilated and warmer environment.

Here are some solutions to help reduce the likelihood of bleeding:

  1. Perform a test on a scrape peice of drywall before proceeding with painting. It is important to also paint over a small test section of dried drywall compound as the problem with drywall staining has not yet been discovered. 
  2. Never add water to the paint as water(latex paints) seems to be the chief catalyst of the problem.
  3. Use the absolute highest quality primer/sealers. It is important to purchase drywall sealers instead of PVA primers. We have not found any significant advantage of using PVA drywall primer. 
  4.  Follow manufacturer's drying times for primers and top coats. if you apply top coats too quickly to wet sealers the tannin will have a medium to travel through and "float" to the surface. 


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