PEG - Polyethylene Glycol - Treatment of Green Wood

[Homer Simpson]

I'd like to know what people's experience has been with PEG - polyethylene glycol, for treating wet wood and minimizing shrinking and splitting. I've found a few posts here referring to it but not much direct conversation about it.

I'm especially interested in its potential application to my own ridiculous project, but I think the subject might be of general interest and this will be good place to put PEG talk.

So what have you done with PEG?

What are the limitations of this material?

What are some good sources for buying or acquiring PEG?

I've heard that it is impossible to overtreat, so it is safe to leave it in longer when you aren't sure of treatment time. .. Is this true?

Xxxxxxxxxxxxxxxxxxxx

I intended for the following to be a reply post, but the posting system automatically merges them:

 

My project entails treating a large chunk of wood, much thicker than the 4" maximum for PEG that I have read about. I have read that the chemical penetrates up to two inches from each exposed surface. My piece is a block, about 10" thick.

I was thinking of drilling an array of 2" diameter holes into the bottom of the block, in such a way that no part of the interior of the wood was more than 2" from an exposed surface. The whole block would be bathed in PEG, upside down so I wouldn't get air pocket in the holes.

Might this work?

[Just Bob]

1 hour ago, Homer Simpson said:

My project entails treating a large chunk of wood, much thicker than the 4" maximum for PEG that I have read about. I have read that the chemical penetrates up to two inches from each exposed surface. My piece is a block, about 10" thick.

I have used PEG for smaller projects, mainly knife scales, the largest was a rifle stock blank.  I am not an expert.  I have not seen any information on the thickness limitation.  My understanding is that the higher concentration of PEG, by weight, the greater the penetration.  The PEG I use is from Rockler and is PEG 1000.  Higher concentrations are sold but I have no experience with those .

The limitations that I know of are: the wood must be green or partially dry.  If your wood is dry you need to soak it in water for a couple of weeks prior to treating. 

You can't use PVA glue.  You are limited to epoxy or urea resin glue.

I wouldn't use it for anything that will have food contact, and you are going to somewhat limited with your finishes. 

@hhh posted some info on PEG under his tips thread ( I think).  The most comprehensive guide I have found, is this one from Oregon State University,  it was written in 1972, but I think the info is still valid, and may help you with your project.

peg.pdf

Tell us what you are going to do with that hunk of wood.

 

 

[mkrusen]

PEG is used in a ton of biochemical and pharmaceutical applications. A lab I worked with uses PEG to encapsulate nanoparticle drugs to "hide" them from the body's immune system so that they can better be delivered to cancer sites. Its a really cool application of the chemical. Sorry, I nerded out there for a second. Never heard of PEG being used in the woodworking world, but its been around for ages and is used all over the place for sure.

[Homer Simpson]

5 hours ago, Just Bob said:

The limitations that I know of are: the wood must be green or partially dry.  If your wood is dry you need to soak it in water for a couple of weeks prior to treating. 

You can't use PVA glue.  You are limited to epoxy or urea resin glue.

I wouldn't use it for anything that will have food contact, and you are going to somewhat limited with your finishes. 

@hhh posted some info on PEG under his tips thread ( I think).  The most comprehensive guide I have found, is this one from Oregon State University,  it was written in 1972, but I think the info is still valid, and may help you with your project.

peg.pdf

Tell us what you are going to do with that hunk of wood.

I'm trying to make a small coffee table out of a single big piece of wood, no joinery. It's just a block with four stumpy legs sticking out. The wood is from a ginkgo tree that was cut down a month or so ago.

I've previously read through most of that same pdf manual you linked. I think that's where I read about the 2" limitation.

 

I had made a thread for discussing this project. I'm not a woodworker and my project was a little controversial:

http://www.woodtalkonline.com/topic/23168-big-ginkgo-blocks/?page=2

 

This was my idea for how the holes would help the PEG penetrate all of the volume of the wood, (with the entire piece immersed, upside down, in a rectagular box only about an inch bigger than the table on each side):

 

[Just Bob]

Ok this gave me something to do at 3 am.  I don't know anything about ginkgo, but the little info I could find indicates that it is a soft wood, and I am assuming porous. So here is my caffeine fueled 3am math.  At 105lbs, it is going to displace a little over 12 gal of water, another assumption here, because the PEG is in solution the displacement should be more.  You would need to find or make a container that fits and holds at least 14 gallons, but I would probably go a couple of gallons bigger.  You should be able to find something that works at a BORG.  According to Rockler, 10lbs of PEG makes 15.4 quarts of 30% or 8.48 quarts of 50% solution.  The higher the solution the greater the penetration, so you would need at least 10lbs but since the soak on this will be around 60 days, you will need more to account for evaporation.  Then you should probably find a submersible heater to heat the solution, I found a couple of cheap ones that heat to 93 degrees, but the guide says 140 is optimal and those got very pricey.  After all of this is said and done you will have to dry the wood and I have no idea how long that would take, but it is at least 6 months, unless you were able to put it in some sort of heated environment.  I would think the drilled holes would help, but that is just a W.A.G. on my part.  Good luck!

 

[Homer Simpson]

23 hours ago, mkrusen said:

PEG is used in a ton of biochemical and pharmaceutical applications. A lab I worked with uses PEG to encapsulate nanoparticle drugs to "hide" them from the body's immune system so that they can better be delivered to cancer sites. Its a really cool application of the chemical. Sorry, I nerded out there for a second. Never heard of PEG being used in the woodworking world, but its been around for ages and is used all over the place for sure.

Yeah I came across many medical products in my searches. Unfortunately those products are even more expensive than the ones advertised for wood treatment, ( I thought I might be able to beat the system by buying industrial). Interesting that the use varies this much and cool that you have that experience with it. 

[Homer Simpson]

11 hours ago, Just Bob said:

Ok this gave me something to do at 3 am.  I don't know anything about ginkgo, but the little info I could find indicates that it is a soft wood, and I am assuming porous. So here is my caffeine fueled 3am math.  At 105lbs, it is going to displace a little over 12 gal of water, another assumption here, because the PEG is in solution the displacement should be more.  You would need to find or make a container that fits and holds at least 14 gallons, but I would probably go a couple of gallons bigger.  You should be able to find something that works at a BORG.  According to Rockler, 10lbs of PEG makes 15.4 quarts of 30% or 8.48 quarts of 50% solution.  The higher the solution the greater the penetration, so you would need at least 10lbs but since the soak on this will be around 60 days, you will need more to account for evaporation.  Then you should probably find a submersible heater to heat the solution, I found a couple of cheap ones that heat to 93 degrees, but the guide says 140 is optimal and those got very pricey.  After all of this is said and done you will have to dry the wood and I have no idea how long that would take, but it is at least 6 months, unless you were able to put it in some sort of heated environment.  I would think the drilled holes would help, but that is just a W.A.G. on my part.  Good luck!

 

Ha ha. Wow, thanks for doing the math Bob.

I am a bit confused by weight, displacement, the amount of PEG required (per units of wood) and the relationship between these three things.

I had assumed the amount of PEG I used would depend on how much void was left in the container I use for the bath. "Displacement" would be a volume measurement of the piece(s) of wood immersed in the PEG bath. What difference does the weight matter?

I anticipated that the PEG solution would dissipate some in the process, from absorption into the wood and from evaporation, and I imagined it would be necessary to top off the bath throughout the process, either with more PEG solution or at least with water to keep the wood fully immersed. .. But is it actually more than a volume measurement of PEG solution? Is the wood absorbing the PEG and reducing the concentration of the solution in the process? .. I have read that PEG may be re-used so I had assumed that it retains its concentration and ratio of water to PEG through each use. .. Is this not the case?

.. Eh and what is a BORG?

[Tpt life]

22 minutes ago, Homer Simpson said:

 

.. Eh and what is a BORG?

Big orange retail giant...an affectionate term for any box store. 

[Homer Simpson]

.. I don't think 10lbs will be enough for me even if I mix at 30%, simply because of the liquid volume. I estimate that my drilled holes alone will take nearly 2 gallons to fill, which would be more than half of a 10lb batch mixxed at 30%.

Rockler sells at $57.99 + shipping and tax for 10lbs. Amazon sells the Rockler product same price but with free shipping..

I'm not sure the specs yet but I found this PEG 3350, 50lbs for $109.99 + estimated $60 shipping, a better deal for that volume:

http://www.nelsonpaint.com/0425E.html

.. The Forestry Service manual on PEG (pdf linked in earlier post) claims that wood is not discolored by PEG. But one of the Amazon reviews of the Rockler PEG says that the wood was badly discolored.

[Just Bob]

5 hours ago, Homer Simpson said:

.. I don't think 10lbs will be enough for me even if I mix at 30%, simply because of the liquid volume. I estimate that my drilled holes alone will take nearly 2 gallons to fill, which would be more than half of a 10lb batch mixxed at 30%.

Rockler sells at $57.99 + shipping and tax for 10lbs. Amazon sells the Rockler product same price but with free shipping..

I'm not sure the specs yet but I found this PEG 3350, 50lbs for $109.99 + estimated $60 shipping, a better deal for that volume:

http://www.nelsonpaint.com/0425E.html

.. The Forestry Service manual on PEG (pdf linked in earlier post) claims that wood is not discolored by PEG. But one of the Amazon reviews of the Rockler PEG says that the wood was badly discolored.

And your freel wood just got expensive!  Welcome to wood working.  The point of figuring out the displacement was to find out the smallest container (in gallons) that would work, if you were to buy it.  I think we both got there just from different directions.  I agree that you need at least 20lbs to make this work.

 

 

 

 

 

 

 

[Homer Simpson]

.. I have read vague descriptions of differing penetration in end grain and side grain, but I didn't account for that in my diagram of holes and PEG coverage. It is more explicitly described here:

http://www.leevalley.com/en/html/05k9805ie.pdf

It says that end grain penetration is up to 2" but side grain is only 1/2" to 1". At that rate my current drilled hole design would not be sufficient, (I was basing on 2" penetration in EVERY direction). .. This document also says that 10 lbs only yields ONE GALLON of 50% solution! Not so sure about that.

.. I think I'm narrowing down the PEG grade and the 3350 linked in my previous post will not be suitable. The number represents the approximate molecular weight and 3350 would be considered very heavy,(large, dense?). It looks like the Rockler product is 1000, which is what I had also previously determined was the best all around weight for this purpose.

It looks like different things could be done with different weights and sequential treatments, if one had the time, money and inclination to experiment. There is an interesting series of observational statements here, with a bibliography, mostly pertaining to preserving archaeological  items of wood:

https://ellencarrlee.wordpress.com/2009/04/08/what-do-we-know-about-peg/

[Addicted Turner]

.. The Forestry Service manual on PEG (pdf linked in earlier post) claims that wood is not discolored by PEG. But one of the Amazon reviews of the Rockler PEG says that the wood was badly discolored.

 

--Its not the PEG itself that will discolor the wood, but if you continue to use the same PEG/water solution for soaking projects, the tannins in the wood will darken the solution completely.  This means that the outer 1/8"-1/4" of the wood will be darkened considerably. I use it mainly for woodturning, so after it dries out, I put it back on the lathe and turn at least 1/4" off of the piece to get back to the lighter color of the wood.  For other types of woodworking projects, you will not have this luxury.   The first few times you use the solution, it won't discolor your work, but after that, it certainly will due to the tannins now present in the solution.