New Wood, MILL GLAZE ? What is it ?

[CedarEd]

Many times I have heard that one should let the New wood weather to rid it of its "MILL GLAZE"
I've heard about Paint Failures attributed to, " MILL GLAZE " What's the story ? Even Norm Abrams on This Old House has done projects where says he is sanding off te "MILL GLAZE" !

[dtnt48]

http://www.wolman.com/pdf/reference/R_3_87.pdf
http://www.fpl.fs.fed.us/documnts/finlines/willi01a.pdf

[Dick Seibert]

This is the main reason I always try to get my redwood resawn, paints and stains adhere much better without the "shiny surface".

[CedarEd]

Mill Glaze, MYTH or Reality, is a MYTH ! The scientists at the Forest Products Laboratory stopped short of declaring that because as scientists they know that it is impossible to prove that something that does Not Exist, Does Not Exist.

This nice convenient and technical sounding term was used to explain paint failures again, and again, and again by Manufacturers of paints, stains and coatings over about 30 years, probably saving them millions. Wood was blamed, wood was the cause, according to these companies. The wood was being coated with a glaze by the mill, the machinery produced a glaze on the wood surface, was their argumant so you couldn't blame the coating they sold you. So companies that invented, sold and profited from coatings they invented for use on wood did not work because of . . . . .The Wood ? ? ? Don'tyaluvit ?

Oh, and IF you can prove that the coating you bought from them failed because of their product failure, no easy task to be sure, What exactly is the Guarantee they give you ? How about a few more gallons for free and not a dime for all the labor needed to strip, often sand, and then refinish the structure.

The Term, "MILL GLAZE" is one reason so many people think Wood is a product that must be high in maintenance.

After attempting to create the mythical Mill Glaze in the Forest Products Laboratory, they asked for samples of mill glaze, and coating failures blamed on 'Mill Glaze', hundreds of samples later, still not a single case of an actual mill glaze. All the failures were caused by known problems like moisture, dirt, application when the temperature was too high, or the wood frozen, or photo deg.

So glad I could explain it to you.

[MarkMc]

Ed, their own publication [Finish Line] states, "This does not necessarily mean that mill glaze cannot happen; it means that we have not been able to duplicate it in the laboratory," and then goes on to talk about surface prep which includes scuff sanding.

See also: http://www.paintquality.com/search.html?q=mill%20glaze

Having produced a "glazed" [or burnished] surface myself, I have seen "issues" in surface finishes when it is not readdressed with some additional surface prep, and would expect any finish that requires tooth or penetration to be questionable. Definitely not lab conclusive nor an indictment of either wood or finish, but rather the process.

Somehow I doubt the group you rep would take a warranty issue beyond replacement of materials, but I may be wrong there. I did replace a couple of glaze defect toilets yesterday from a manu located not too far from the FPL, and they too stop at product replacement, though I may get a free calendar or something from the area rep or perhaps a new seat. ;)

[mike maines]

Ed, have you ever used red cedar lumber? It often has a glossy surface, presumably from dull planer blades or possibly from "caramelizing" of sugars in the wood during planing. It shows up as "flashed" paint, which are glossy areas that show through the finish coat, or sometimes the paint will peel. A quick sanding takes care of it.

[Tom Bainbridge]

CedarEd, cowboys have always and will always hide behind urban myths

capitalist cowboys aint stupid, they know that lenin. the ultimate communist, was right

"repeat a lie often enough and it becomes the truth" i come across it far too often

[Lavrans]

I agree with Mark.

I've milled enough to have burnished some product (when the blade gets dill and the surface is burnished rather than cut). I have gotten millwork from suppliers with a little burnish, which is what I was taught "mill glaze" was.

Really, though, anything should be sanded first because, to my knowledge, all the millwork out there today is produced by round cutting blades. That leaves cutter marks. Even if they're hard to notice, they do telegraph, and sanding will produces a smoother finish.

Some mysterious "glaze" isn't going to be common enough to be a problem. More often I'd bet the product got contaminated in shipping or the painter didn't prep very well. Even a burnished piece will hold paint to some extent; you can often see it when finishing with say, Tung oil because it won't soak in as well and will stand out from the surrounding, non-burnished wood.

[aerieandy]

Not that I don't believe the paint people wouldn't use a myth to further their ends, but there is definitely something to it. If you don't believe a burnish or glaze affects adhesion try glueing up two burnished surfaces with "mill glaze" and two that have been given some tooth with light sanding, and see which joint is stronger and permanent.

[CedarEd]

I work for the cedar mills, I know a fair bit about Western Red Cedar, and sorry no mill glaze. The Forest Products Lab is simply saying, "If it exists, we haven't seen it yet.!" because they are scientists and despite the fact that they did everything and anything they could imagine to create the mythical Mill Glaze, they did not, and could not. They also asked for and got hundreds of samples of coatings failures all attributed to the non-existent mill glaze, and still, No Mill Glaze. Not one time ! That's a pretty good lack of evidence and these boys know more about wood than you'd ever want to know.

The ideas about dull planer knives, also doesn't wash, the FPL tried that on many different wood species, also high speed planers and molders and low speed. I spent 11 years working for the Rolls-Royce of Western Red Cedar mills, a place where the planer knives were kept flawlessly sharp, and the feed speeds slow, so the 'knife marks per inch' were impossible to count. People often asked us what finish was on the wood, there was none. The WRC was then packed into 20' long 4' wide cartons that had to fold differently for each size lumber they were packaging, and the boards were each packed one piece at a time, by hand. Then a cover went on the box that contained 1000 bd.ft. of Western Red Cedar, and all the reinforcement to hold it together went on the outside with corners and one inch boards under the strapping so it did not get marred. This is not mill glaze, it is high quality, and cedar mills do it more often than most because Western Red Cedar is always used for its appearance.

Now the FPL did another bit of research and discovered that the best surface to have if the wood is to be finished is, in order of preference:

1- a Planer smooth surface that is subsequently sanded with Medium, not fine paper (60-80 grit)
2- A Roughsawn surface created with a saw blade not a moulder or planer
3- a smooth planed surface straight from the mill.

Coatings have failed on wood for discernable, and identifiable reasons, but Mill Glaze is NOT one of them.

[tom struble]

it's good your here Ed, everything i thought i knew is apparently wrong

actually my next siding job is a wrc vertical t&g job followed by a cedar shake job,i appreciate the info

[No faux zone]

I'm going to follow the directions of the paint company when I paint, not the milling industry. the FPL isn't going to be the one coming out to my job if my paint is pealing off the house.

I'm not sure what the point of this is.

[MarkMc]

Coatings have failed on wood for discernable, and identifiable reasons, but Mill Glaze is NOT one of them.

"This does not necessarily mean that mill glaze cannot happen;...
http://docs.google.com/viewer?a=v&q=...kSrvGiQMW9pOQw

Like you said, the scientist led panels speak very carefully.

Answer us this, in all those tests done in attempting to isolate "mill glaze" as a failure point for coatings, what prep practices were followed and what range of finishes were applied? Seems the argument is over whether the product is bad or the prep was insufficient.

A condition known as mill glaze (also called planer’s glaze) can occur on smooth flat-
grained western redcedar siding and occasionally on other species, such as redwood.
There is controversy over the exact cause of this condition, but it seems to be a result of
using dull planer blades and is exacerbated by the difficult-to-plane flat-grained surface
lumber. In vertical- grained wood, the earlywood/latewood bands are perpendicular to the
surface. Because of this perpendicular orientation, vertical- grained lumber is easier to
plane, even with dull tooling. Planing causes two distinct changes to the surface of the
lumber — it burnishes the surface and crushes some of the wood cells.

During the planing or milling process, overheating of flat-grained siding may bring more
water-soluble extractives to the surface, creating a hard, varnish- like glaze. Excess
water-soluble extractives can also form on the surface during kiln drying. As these...

http://docs.google.com/viewer?a=v&q=...WIyFa2X6yqSF5g

[No faux zone]

I've really never thought about mill glaze being a problem. In my world it's expected to have a certain amount.

Every paint manufacturer I know of recommends that all bare wood be lightly sanded and then primed. I think if you follow that recommendation you should have little issue with coating problems. If a problem does occur, it's most likely going to have something to do with moisture content of the wood, surface conditions, or practices used by the painter.

The milling process or imperfections by the mill would be about the last thing on my list to go to when it comes to paint failure.

[Lavrans]

I work for the cedar mills, I know a fair bit about Western Red Cedar, and sorry no mill glaze. The Forest Products Lab is simply saying, "If it exists, we haven't seen it yet.!" because they are scientists and despite the fact that they did everything and anything they could imagine to create the mythical Mill Glaze, they did not, and could not. They also asked for and got hundreds of samples of coatings failures all attributed to the non-existent mill glaze, and still, No Mill Glaze. Not one time ! That's a pretty good lack of evidence and these boys know more about wood than you'd ever want to know.

Coatings have failed on wood for discernable, and identifiable reasons, but Mill Glaze is NOT one of them.

Well, you're just talking about Cedar now, and I've never had any problems with Cedar.

That said, really prefer to buy pre-primed Cedar from a good local source.