Silicon

[doorstop]

http://media5.hypernet.com/~dick/ubb/frown.gif I painted the outside of the hull before my boys got home for the end of term break and they are varnishing the topsides. First race etc. next weekend... However, the previous owner(s) have used silicon sealer all over the place and the varnish is 'shrinking' away from the damned stuff! Does anyone have a magic solution for getting rid of it, I/we have sanded back to bare timber but to no avail... HELP!

[paladin]

Paint should go right over silicon.....it's just sand. What you have is SILICONE....and once that stuff gets on anything you may as well burn the boat. If it were F******stuff you might be able to use some really strong cleaners to get it off, but wood or anything porous......it holds like grim death. Just my opinion. http://media5.hypernet.com/~dick/ubb/biggrin.gif

[Paul Hughes]

If its any help I have some stuff called “Silicon Eater”.Made by Ever Build Building Products Limited.Troydale Mills,Troydale Lane, Pudsey Leeds LS28 9LD. Phone uk1013 255 0033. It worked well on my windows.
Paul

[Charlie J]

In the furniture shop, we have difficulties with silicone contamination also due to furniture polishes that contain silicone. For lacquers there is a product known as "Fish-eye Killer" made to stop the rejection of finish caused by silicones- normally found as little round spots we call fisheyes. Basically, it's a dilute silicone itself mixed with the finish. Don't know if it'll work with varnish but I use a product called "Smoothie" that I get from an auto paints place. I'd phone the maker of your varnish and ask if it's compatable. Number should be on the can. I wouldn't use in in all the varnish - only in that needed to over coat the problem areas- you don't want to spread the problem over all the wood.

Good luck - the stuff is really frustrating sometimes

[Jamie Hascall]

We've found that the essential oil of orange cuts through silicone that has been used to glue down pieces of art glass. I have never tried it to remove silicone from a porous surface and have no idea if further problems may arise from contamination with the orange oil, but it may be worth a look. I may need it next year when I redo my ports and windows, many of which were sealed with silicone.

Jamie

[ken mcclure]

Has anyone tried shellac over silicone? Or shellac under varnish on a boat? Shellac seems to cover almost anything, and to provide a decent barrier.

[Tom Dugan]

Good question, Ken. I've just completed finishing a mahogany hollowood tube (http://www.brandnew.net/hollowood/holomore.shtml) with several coats of Captain's varnish over 2 coats of shellac over aniline dye. There are no adhesion problems between the shellac and varnish, which is to be expected. If memory serves, I have read of shellac acting as a barrier over silicone, but I hope somebody else can confirm or deny.

-T

[Billy Bones]

I've had good luck getting rid of minor silicone incursion into wood by using stripper. Sometimes a few tries are necessary to get it all.

Jamie's comment is very interesting. Perhaps 'Citri-Strip' would be doubly effective in cutting the stuff.

At any rate, with patience you'll solve the problem.

BTW, Sanding the stuff off only smears it around more. Stripping, using a brass brush to work into the grain and washing the wood frequently with TSP is much better. Once your satisfied you got it all, then sand.

Shellac seals out most things, but not silicone in most cases.

Good Luck!

[Nicholas Carey]

Originally posted by doorstop:
However, the previous owner(s) have used silicon sealer all over the place and the varnish is 'shrinking' away from the damned stuff! Does anyone have a magic solution for getting rid of it, I/we have sanded back to bare timber but to no avail... HELP!

It sounds like the dreaded fisheye disease to me (probably silicone contamination). Here's what it looks like:

http://www.taunton.com/finewoodworking/media/w00001_11.jpg

Here's a link that you may find of use at tracking down the source of contamination -- http://www.woodweb.com/knowledge_base/The_Great_Fisheye_Hunt.html

Fine Woodworking a while ago published this article, A Primer On Sealers at
http://www.taunton.com/finewoodworking/pages/w00001.asp, which has this to say about fisheyes and fixing the problem:

To provide a barrier coat -- Waxes, polishes and silicone residues encountered when refinishing furniture can cause contamination problems such as fisheyes, which are small craters in the finish film. You can remove wax by wiping stripped surfaces several times with naphtha or mineral spirits, but silicone is impossible to remove completely. It has a tenacious ability to remain in the pores of wood.

To remove fisheyes, immediately wipe off any wet finishing product (oil-based stains will develop fisheyes, too) and wash down the piece with mineral spirits or naphtha. Then scrub it well with TSP (trisodium phosphate) or a TSP-substitute and the green colored Scotch-Brite nylon pad. After that, apply a freshly made coat of dewaxed shellac to seal in the contamination.


Why shellac? because it's a great sealer. It sticks to almost anything and it's compatable with virtually any finish, either as a sealer or as a tie coat. I probably wouldn't apply 2-part poly finishes over it, though -- Never tempt the gods.

Bear in mind that you really should mix your own shellac rather than buying pre-mixed shellac.

Why? Because fresh shellac is waterproof (think of what it is, the shell of the larvae of a tropical beetle (the Lac Beetle. Who could make this up?) Producing a non-waterproof shell for your larvae is not exactly a survival trait.) In contact with alcohol it esterifes, becoming softer and susceptible to water damage. After a month or two in an alcohol solution, the shellac finish will be susceptible to water damage.

Shellac flakes (and a lot of information) are available from, among other places,

* http://www.shellac.net
* http://www.hocktools.com
* http://www.woodfinishsupply.com

You can get shellac as well from Woodcraft Supply, Highland Hardware, Rockler Hardware, Garrett Wade, etc.

[thechemist]

Odorless mineral spirits is mostly aliphatic hydrocarbons...straight and branched chains and napthene. Aromatic naptha is aromatic rings with side chains and stuff on them, and these are two different things. Xylene is a very light[smaller-molecule, faster-evaporating] version of aromatic naptha, and if you cannot get aromatic 100 or 150 you might try Xylene, for it is mainly aromatic 100 that swells silicone rubber and weakens it so it comes off of a surface to which it is stuck with only a light scrubbing with a Scotchbrite {tm} pad.

I know about this because some years ago I did the research for doing exactly this sort of silicone-rubber-residue removal. I tested every sort of chemical known to man or beast, and only two things worked. One was incredibly caustic organic amines, and the other was Aromatic 100.

Aromatic naptha may be commercially available in small quantities, but not all kinds of naptha [petroleum distillate] will work, as above. Xylene is the closest and is often sold in paint stores.

[ken mcclure]

Whew! Get yourself a mask if you're gonna work with the Xylene. Stinky stuff.

[bainbridgeisland]

I have used Xylene to remove silicone finish on synthetic ropes before potting them in place. It works pretty good, though I am always looking for something better.

[NormMessinger]

Mr. Chemist, when you talk about silicone rubber does that include silicone as in some polishes and spray lubricants?

--Norm

[Bob Cleek]

Oh, boy... I learned about "silicone fisheyes" the hard way. The prime suspect? WD-40! I used to spray that stuff on everything around the shop. Kept a couple of cans handy all the time. It seems even the fine mist that enters the air can land on finishes and getting rid of it is really difficult!

[thechemist]

Norm...silicone oils are different from silicone rubbers. An oil is a liquid and will spread into a thin film. A rubber is a solid, stuck in one place.

Aromatic solvents such as xylene [Aromatic 100 is much better....] will dissolve silicone oil, it just takes many successive rinsing/wipings with clean paper towels moistened with fresh portions of solvents.

This solvent causes the rubber to release fairly readily...it is absorbed into the rubber and causes tremendous swelling and physical weakness, and then Scotchbrite(tm) or even a plastic pot-cleaner takes it off a surface [such as porcelain] .

This family of solvents also dissolves silicone oils, which many solvents do not. It requires a solvent or solvent blend which is capable of dissolving the offending species to remove it.