"lab test"

[Mountain View 14]

Ok folks, this is my first “lab test” using two panels of a fence between my neighbors house and mine. I would welcome comments about what I did right and/or wrong. Remember, I’m still new to this, try not to flame me too bad.

Specifics:

Fence is about 6 year old cedar (I think), never treated, faces east with not very much direct sunlight. Grayed with some mold and algae.

Left side was treated with percarb mixed 6oz/gal and allowed to soak for 15minutes. It was kept wet with product to stop it from drying out.

Right side was treated with 1.5% sodium hypochlorite (6% cut 1:3 w/water). It was allowed to soak for 15 minutes and kept wet with product to stop it from drying out. I haven’t been able to source 12.5% liquid product yet, hope my math is right.

Both sides were rinsed with a 3700psi/4gpm cold-water unit with a 25 degree #12 tip for five minutes. I held the tip no closer than six inches from the wood, usually 8-10 inches.

Oxalic was applied to both sides (3 oz/gallon), kept wet, let dwell for 10 minutes and rinsed the same way as above.

To say this stuff furred up is putting it mildly. Did I do something wrong? Did this happen because it’s old, untreated, and probably low-grade wood? Is sanding/defurring just something that needs to be done in this case? I’m trying to do this right, so if I’m going down the wrong road, I’d like to be corrected and adjust the way I do things sooner rather than later. Thanks for the help.

[Mountain View 14]

Close ups. Hope these show up ok.

Left is bleach, right is percarb

[Mike Stahmer 14]

Hey Pete,

First off when cleaning wood, you really need a pressure guage and use as little as pressure as possible. Its alot easier to increase cleaner strength than it is to get all those fuzzies off. I usually never go over 1100 psi on fences and that is max. I also use a 40deg tip. With the proper cleaning agents applied, you really just have to basically heavy rinse it with the pressure washer. Also, using the proper tip when going down on PSI helps out. This way you can maintain high GPM with low PSI. I believe I use a 7.5 nozzle for wood. I can get 1000 psi and 4.5 gpm out of it I think!

[Mountain View 14]

A #12 tip brings me down to around 500psi at 4gpm right??

[Deck Guy 14]

Hey Pete,

First off when cleaning wood, you really need a pressure guage ...

Can't you just do the math once, and use the proper tip (or keep several on hand with the knowledge of the PSI they produce)? Science RULES! I generally use a 4010 tip for all decks, which gives me about 600PSI.

Here's a link to a nozzle chart at RPC:

http://www.rowlettpressure.com/nozzlechart.htm

I use the same machine for every deck, so why would I constantly check the pressure?

[Mike Stahmer 14]

WHy would you not have one! I adjust the pressure often for different woods! It's only ten bucks and that way you can be more versatile and consistant with your washer. Have you ever not cleaned something else with yours? I use mine for various cleaning jobs and need to know what pressure I'm at for consistancy! Doing it by feel can lead to trouble one day when you gouge a deck because you cleaned concrete earlier in the day at another pressure!

[FullBlast 14]

WHy would you not have one! I adjust the pressure often for different woods! It's only ten bucks and that way you can be more versatile and consistant with your washer. Have you ever not cleaned something else with yours? I use mine for various cleaning jobs and need to know what pressure I'm at for consistancy! Doing it by feel can lead to trouble one day when you gouge a deck because you cleaned concrete earlier in the day at another pressure!

I do have pressure guages on most of my machines but never use them to check it between different jobs. If you go from concrete to wood in the same day you just come into the wood slow till you get the feel of it and find out how hard you have to hit it. Just my thoughts!!

[Mike Stahmer 14]

That is true! I just prefer my guage! On a redwood deck, there is alot of difference between what 900 psi and 1300psi can do! Trying to figure out where your at costs time, and possible more fuzzies that you have to remove. I just prefer to know exactly what I am cleaning at for reference etc! I have mine quick connected right after my injector so it isn't much trouble to use!

[Littlefield 65]

Mike, is that near your gun or the machine? it would be kind of cool to have one right there on the gun to see all the time, esp. when using a variable pressure wand like I have....

[Mountain View 14]

Ok, I forgot to put my pressure guage on to check things. My bad. But what about the wood? I did another part of my yard without this problem which makes me thinks at least some of the issue is down to the low grade of wood. Lesson learned.

[James 625]

Mounty give me a call tommorow 203 558 0968- no problamo

[Mike Stahmer 14]

Mine is on th e machine but sure, you could mount it quick connected behind your gun! I know a couple guys that do that!

[PressurePros 249]

Cedar is brutal. I really dislike it. It's funny, I just read that someone likes the look of cedar with all of it's knots. I think it looks cheap. Personal preference I guess. Anyway, your nozzle choice was right on except I would use a smaller orifice with a wider spray pattern to work faster. The amount of knots per linear foot on that cedar indicates a pretty cheap grade. I think just the age, exposure and grade were the factors that caused your furring.

[squirtgun 122]

We don't do the wood thing much anymore but, when we did we invested in a gauge for the machine,as well as,over sized tips to lower the psi.You learn quickly what size tips will deliver the desired psi.

Besides I thought cranking the psi up and down with the unloader was bad for the machine and pump.

[big mike 14]

Pete,

I noticed several things that should be pointed out. First, Sodium Hydroxide wasn't necessary if it was just graying wood with some algae. Also, Percarb mixed too strong will result in furring. A simple bleach bath followed by an Oxalic rinse would have been the easiest in my opinion. There's a great debate concerning bleach on this forum, and I don't want to start that up again. Anyway, I think a 25 degree tip is too intense for wood restoration and that was a large factor in the furring you experienced. 500-700psi with a 40 degree tip about 12 - 15 inches away from the surface, and about a 3-5 minute dwell with the chems would result in substantially less furring. If your not stripping off an old finish, all you basically need to do is wash the fence and brighten. Also, I never sand fences.

[Mike Williamson 198]

WHy would you not have one! I adjust the pressure often for different woods! It's only ten bucks and that way you can be more versatile and consistant with your washer. Have you ever not cleaned something else with yours? I use mine for various cleaning jobs and need to know what pressure I'm at for consistancy! Doing it by feel can lead to trouble one day when you gouge a deck because you cleaned concrete earlier in the day at another pressure!

Most of us just regulate the pressure with various tips, not messing with the unloader. I know what tips give me what pressure. I've been doing it "by feel" for a good while now and haven't been led into any trouble!!

[Deck Guy 14]

I didn't say I don't have a pressure gauge.

I tried to say that I don't need one to measure the pressure when I can use the scientific method (or a simple chart based on the formula) to deduce it. No-one said anything about working by "feel." To me, the math is the math. Two plus two always equals four. Maybe you're more comfortable looking at a gauge. So be it.

There are times when they are necessary (maintenance, etc...), they're just not needed to figure what PSI a given tip produces.

[Adrian 155]

So Have I been doing it all wrong using my zero degree tip at 3500 psi.? It only takes me about 7.5 hours to do a 150 sq. ft. deck and my time is improving. I usually just dump out a 5 gal bucket with 12% straight and follow it all up with muratic brightener and rinse with my dual turbo nozzle at 3500 psi.

The plants below seem to just love the mix and you can't beat the grooves left behind in the finish of the boards afterwards, because the water just seems to fill the grooves and run off the deck. But the best feeling of the job is that wonderful haze left behind when it all dries and you have a grateful customer.

I'm sorry,

just been one of those days, please don't kick me off of the forum.

I'm trying to laugh it off.

..... other uses for Pw hose = noose!!!!

[Mike Stahmer 14]

That is pretty funny! I think we've all had those kinda days! I'm laughing my A** off! "A noose" LOL.

[John Orr 206]

OK, here is my 2 cents... I think you may have used too little psi! 500 psi, from a distance (there is a formula to calculate psi drop over distance sprayed, but I don't know it) is, for me too little. The gray I see in the pics indicate the old graying is still there. Just a little more psi should do it. (I generally use a 10 tip.)

It would also appear that the SH was too weak, I have no experience with percarb, so I can't even guess what happened to that section. If I am not stripping a fence/deck,I will downstream SH (I use RPC Roof Magic)and I apply the oxalic with a backpack sprayer.

[Jarrod 22]

Apply Sh, Low Pressure Wash, Then Apply Brightener. Simple.

[RCBill 14]

I am having similar problems with a cedar fence, mine. This is a lab for me also, I've used a number of different cleaners/strippers.

I have been of the opinion that I need to knock the UV damaged wood off. It seems to me that 1) it is impossible to do this without getting furring, and 2) I would think excess stain would collect in the lightened, but spongy damaged material left in place. Please post your comments.

Rod has posted that for severly damaged wood he recommends a semi-transparent stain. My experience with coatings is that you just can't put everything on anything. Do any readers specify different coatings based on conditions? Or do most stay with one finish and make it work?

I put my cleaners/strippers on dry wood. Is that the way you apply yours?

TIA,

Bill

[Paul B. 523]

When you regulate pressure with the unloader, you are also changing your water flow rate. You should use different sized nozzles to increase or decrease your pressure without changing your flow rate (GPM).

A #12 nozzle running on a new 3700psi 4gpm unit should yield about 500 psi with the unloader fully opened.

You will also have a pressure drop of about 100psi for every 100 ft of 3/8" diameter high pressure hose.

A #12 - 25 degree nozzle will provide the same pressure as a #12 - 40 degree nozzle. In otherwords, there should be no pressure change, only the coverage area changes.

Cedar is a very soft wood and will furr easier than most other types of wood.

Allowing wood to gray will destroy the adhesion of wood fibers (which is one of the cause/effects seen in furring). Chemicals such as bleach/pool shock, sodium hydroxide, percarb left on too long will also cause excessive furring.

In otherwords, aged wood will be furred and this will have to be removed without causing additional furring by too high pressure, too strong chemicals or too long of a dwell time.

In this case it is possible that not enough pressure was used to remove the dead fibers. There is usually a fine line between removing loose fibers and causing furring. This is more of the art portion rather than the science portion of the job. Experimenting with changing pressures (nozzle sizes), chemical mixes (dilution ratios) and dwell times will tell you how you need to deal with different types of wood in your region of the world.

[RCBill 14]

I tried a number of different solutions. The surfaces with the least fuzz were treated with either simple Percarb or EFS-38. I used a 25 tip and was pretty aggressive, knocking the dead stuff off. I got in trouble with the HD-80, CPR, and some pretty hot bleach.

A second problem is that the fence is a shadow box. Had I been working on a simpler design, I could have buffed the Percarb and -38 treated surfaces and used RS. My test spot with RS looked pretty good, looking past the fuzz.

In summary, I think that my problem was solutions that were too hot for my application, not too much pressure.

A process that I did not try that someone, maybe Jarrod, posted was prewetting the wood before application of the cleaners. Could someone elaborate on this?

I appreciate all the input from everyone on this. Even a phone call with Shane. Real professional group here.

Never felt this good about having a problem with a job.

Bill

[PressurePros 249]

When you regulate pressure with the unloader, you are also changing your water flow rate. You should use different sized nozzles to increase or decrease your pressure without changing your flow rate (GPM).

While the basic premise of using the unloader to control pressure is not a great idea, it's actually fine to turn down the unloader to match the pressure of your output. You will not lose any flow.

Example: You use a number ten nozzle to achieve your pressure, say 1000 psi. Using a pressure guage, you can back off the unloader until the pressure begins to fall below 1000 psi, then just turn it back up a quarter turn.

[Mike Williamson 198]

While the basic premise of using the unloader to control pressure is not a great idea, it's actually fine to turn down the unloader to match the pressure of your output. You will not lose any flow.

Example: You use a number ten nozzle to achieve your pressure, say 1000 psi. Using a pressure guage, you can back off the unloader until the pressure begins to fall below 1000 psi, then just turn it back up a quarter turn.

I know this has been debated before, but I disagree. Your pump puts out a certain amount of water, say 5gpm. That water has to go somewhere, whether it is flowing out of the trigger gun or going back to the tank via bypass. If you're using a #10 nozzle to get 1000 psi, then all the water is flowing out of the trigger gun. If you then back the unloader down to where you're only getting 500psi from the trigger gun with a #10 tip, then you only have approx. 3.5gpm coming out of the trigger gun. The other 1.5gpm has to be going somewhere, and it can't be out of the trigger gun, our you'd still have 1000psi. It HAS to be bypassing.