The primary reason for varnish lifting is a poor surface for the varnish to bond to. The contamination can be from excessive moisture, oils, decay, dust, excessive PH, or all of the above. Teak cleaners are very acidic. They dissolve the connective tissue (between the growth rings) of the wood and leave the wood soft and porous. Brushing with a deck brush or scrubber further removes the soft parts of the wood. After years of this the teak is left with ridges. This is very common on teak decks when oil is used. Oil traps dirt necessitating frequent cleaning. The roughness and chemicals from the cleaners trap moisture and dirt in the grain. Over time the moisture and chemicals dissolve the bond that holds the varnish and the varnish peels.
Another reason for varnish failure is too little varnish on the wood. Varnish has ultra violet light absorption particles. After a while these particles break down from absorbing the light. Once the break down occurs the varnish yellows and develops cracks allowing moisture to seep into the wood causing the varnish to peel. Excessive sanding between coats of varnish advances this problem. Five or six coats of varnish may be applied, but the sanding only leaves a two coat thickness. The thinner the coating the faster the varnish will break down from sunlight.
My outline "Brightwork; Give one weekend, get years of beauty" addresses application procedures so to reduce or eliminate the above problems.
The Back to Nature stripper is PH neutral and washes with water leaving the wood without lifting the grain or softening the sapwood. The sanding with a hard sanding block will take down the ridges without removing the soft wood between the grain ridges and prevents wavy scalloping along the length of the rail. Soft sanding block or hand sanding should only be used with the finest grit sandpaper and on curves. Finally the use of CPES cures any problems with the wood condition. It removes excess moisture, dissolves wood oils and incorporates the oils into the epoxy, and restores the lost strength to the sapwood. The long cure time of the CPES allows a "green" time between solvent evaporation and full cure. This green time is when the varnish or paint should be applied. The green time allows a molecular bond to occur between the varnish and the epoxy and the wood, glueing the coating to the wood. Applying varnish directly (without sanding) over the "dry to touch" CPES eliminates excessive dust contamination.
As long as a proper thickness of varnish is applied and maintained you should never have to strip down to bare wood. When applying varnish scuff up the surface between the first three or four coats in stead of sanding. Use a 3M-07447 Scotchbright pad (does not leave residue) and leave the edges. After the fourth coat sand using a hard sanding block and 180 grit paper to level the surface. Add two more coats scuffing between. Finally sand with 200 grit and apply one more coat. Make sure to strain the varnish for every coat, wipe the dust with an alcohol soaked rag and finally a tack rag.
I suggest Bristol Finish due to it's durability, application ease, and long lasting capabilities. The above application description is for traditional varnishes. Bristol Finish is a little different since sanding is not necessary between coats.
As a rule of thumb; If water can get under, it will cause decay and peeling. Do what you can to make sure the piece is properly bedded and varnished.
The author, Steve Ray, is President of Star Distributing and has over 20 years of experience maintaining brightwork.
Ready-Strip® Marine is trademark and manufactured by Back to Nature Products, Englishtown NJ
Clear Penetrating Epoxy Sealer, CPES is trademark and manufactured by Smith & Co. of Richmond, CA.
Bristol Finish is trademark and manufactured by C Tech Marine of Melbourne FL.
3M-07447 Scotchbright is trademark and manufactured by 3M corp., St. Paul MN
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