# Picnic table finish



## 6SpeedSD (Jan 21, 2011)

I'm getting ready to build 4 picnic tables for a relative of mine. I've heard that you shouldn't use pressure treated lumber because the chemicals can be released over time and make people sick when eating off them. If that's the case, then what route should I go to seal them from the elements? I most likely just use construction grade lumber (2x4's, 2x8's, etc). Can I just seal it with some Thompsons, or should I use like a spar urethane?


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## sawdustfactory (Jan 30, 2011)

Depends upon the look you want. I'd go varnish if you want it to last. Having done several picnic tables over the years, I suggest you build then disassemble to finish, then re-assemble...will make life so much easier.


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## 6SpeedSD (Jan 21, 2011)

Looks aren't really an issue. Longevity is. I'm sure at some point my dad will end up using them as a work table because it's too convenient!


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## cabinetman (Jul 5, 2007)

6SpeedSD said:


> I'm getting ready to build 4 picnic tables for a relative of mine. I've heard that you shouldn't use pressure treated lumber because the chemicals can be released over time and make people sick when eating off them. If that's the case, then what route should I go to seal them from the elements? I most likely just use construction grade lumber (2x4's, 2x8's, etc). Can I just seal it with some Thompsons, or should I use like a spar urethane?


You could use PT. Several years ago the treatment no longer used CCA (arsenic), but now uses a copper based treatment. As for safe as a dining table, unless you spread your food directly on the table and eat it that way you have no worries. Using plates is the preferred method for serving food.

Treated with an oil finish will provide an easier maintenance than a film finish like a spar urethane. Use an oil that's recommended for PT. You could use Penofin Red label, or Wolman Oil wood preservative.












 







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## Brink (Nov 22, 2010)

Film finishes will eventually fail, then they need to be stripped and reapplied.

When an oil finish becomes worn out, just scuff an reapply. It's a lot easier in the long run, IMO.


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## 6SpeedSD (Jan 21, 2011)

So basically I can just build with PT lumber. That alone will outlast the amount of time those tables will be used.


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## ShavinWood (Mar 30, 2011)

*Possible options*

Some potential options for avoiding PT lumber - 
Wood preservative/fungus inhibitor
Borax
4 lb.
Boric Acid (Roach Kill) (Dollar Store Item) 
3.5 lb.
Propylene glycol (potable water systems anti-freeze, boat/RV) IMPORTANT NOTE: DO NOT USE AUTOMOTIVE ANTIFREEZE IT IS A DEADLY POISON AND EVEN SMALL AMOUNTS WILL KILL YOU! 
1 gal.


On an outdoor stove bring antifreeze to low boil in an old stock pot (camp stoves work well)
(THE PRODUCT CONTAINS ALCOHOL – BOILING INDOORS IS DANGEROUS). Add Borax and stir well, then add Boric Acid and stir on low heat until the mixture is fully clear. Using gloves apply with sponge when cool enough to handle safely.

This is a strong wood preservative that repels insects while considered reasonably safe for humans and pets. Propylene glycol (REPEAT: Potable Water Systems boat/RV Anti-Freeze only) seeks out and bonds to moisture. In this mixture it pulls the Borax/Boric Acid with it deep into wood pores where the combination bonds to provide thorough preservation. The product is also beneficial for inhibiting further deterioration of wood that has been neglected. 

Stored product will re-solidify, re-heating until liquid and clear again allows stored product to be used again. 


Outdoor penetrating wood finish

Spar Varnish or Spar Urethane 
3 cups
Boiled Linseed Oil 
1 cup
Pure Paraffin Wax
1.5 oz.
Mineral Spirits
1 gal. (- 4 cups) 
Oil Stain of Choice
1/4 to 1/2 cup



Thinly shave wax into Mineral Spirits. Add Spar Varnish and Boiled Linseed Oil. Allow to sit 
Overnight and/or shake well until wax is completely dissolved. Warmer conditions help speed up 
the process. Add oil based stain if/as desired but only to finish that will be used immediately 
(stain in finish that is stored will seperate out and solidify in just a few days).
Apply liberally spring and fall with a sponge. 


This is a penetrating finish, not a film finish so it doesn’t flake off. The natural look/feel of the 
wood is retained. The finish is absorbed into the wood where it seals the pores. Water will 
Water will bead like a car’s finish for months but the surface is not slick. It makes a good finish 
for porches and decks however in freezing temperatures frozen water beads on the surface can be 
slick.


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## gus (Oct 31, 2010)

personally i would not use pt for a picnic table. it just doesn't look very nice. i would use redwood or cedar to construct it. either of those will hold up to the elements and come in 2x sizes.


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## Brink (Nov 22, 2010)

5/4 Ipe (mahogany) decking works nice, too.


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## fromtheforty (Jan 15, 2011)

Shavin Wood,

Is the oil stain of choice in the "outdoor penetrating wood finish" a deck stain or a colorant stain of your choice to give the mixture a tint that you like? 

At one time, someone was telling me about a similar mixture that the US Parks Service uses. Is this that recipe? Thanks!

Geoff


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## cabinetman (Jul 5, 2007)

Brink said:


> 5/4 Ipe (mahogany) decking works nice, too.


Ipe and Mahogany are different woods.












 







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## mancavewoodworks (Mar 5, 2011)

personally, pressure treated is ok for the legs, but i would use cedar, cypress, redwood or white oak for the rest. with no finish at all. if weight is a problem, use cedar or redwood!


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## Brink (Nov 22, 2010)

cabinetman said:


> Ipe and Mahogany are different woods.
> 
> 
> 
> ...


Yeah, I know...a lot of lumber yards around here call any tropical hardwood, especially for decks, mahogany.


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## ShavinWood (Mar 30, 2011)

*Preservative/Sealant Follow Up*

Geoff,

The oil stain referred to in my post is colorant stain to achieve a desired color tone i.e., Minwax, Cabot, etc. As indicated these should only be added to finish that will be used within a day or two. Applying the finish without added color will permit natural graying of wood while still offering protection from water damage. 

To be clear, it’s not a new magic formula, as I understand it, The US Parks Service uses a similar finish, however this formula incorporates Boiled Linseed Oil to slow drying and enhance penetration/bonding. The addition of Linseed Oil also helps stabilize the product somewhat - allowing for the use of a higher volume of Paraffin Wax (beneficial for sealing wood pores) and slightly extending the time that oil stain colorants remain stable in the liquid.
The end product provides protection similar to a Sikkens or Thompsons but at significantly less cost, and in my personal experience as good if not superior protection. 

The Borate solution listed as a preservative is also nothing new or exotic. It’s simply a home brew of commercially available Borate solutions used in more natural wood preservatives/insect repellents for a long time. I use it when air drying lumber to avoid/stop dreaded insect infestations. The only real difference in this case is cost.

I’ve attached some Pics. of a project completed last fall that shows combined preservative and sealant performance in both wet and dry conditions. A reapplication of sealant will be scheduled as-soon-as the weather improves and again in the fall. Despite the harsh winter the porch/exposed deck surfaces are still beading water. As indicated previously, the only complaint is that water beads freezing on exposed surfaces are very slick. This problem was quickly addressed by using open grate rubber mats that are simply lifted after the threat of freezing. 
ShavinWood
(Tom)


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## Lola Ranch (Mar 22, 2010)

gus said:


> personally i would not use pt for a picnic table. it just doesn't look very nice. i would use redwood or cedar to construct it. either of those will hold up to the elements and come in 2x sizes.


+1

Bret


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