O.K. whether it’s paint of varnish, there comes a point where it is just got to come off. If it is varnish, at least you can see when the wood-to-coating join starts to breakdown. If it’s paint, you can’t see when it is going wrong until the wood is entirely saturated underneath and starts to create bubbles of water under the varnish.
How you take the varnish off will largely depend on what it is you are trying to take off and how well it is presently attached to the wood.
If it is really bad, lets face it, it can be just dropping off which is a good start, but to be honest, if the varnish is that loose, you have to be rather worried about the quality of the wood underneath, how long has it been standing around with no protection at all. I would have a good look and just make sure that is not going to be easier to replace the wood entirely.
There are various ways of removing paint/varnish. You can sand it off, scrape it off or burn it off….with chemicals or hot-air. I normally end up using most of these methods….even on the same bit of wood. Sometimes one thing works well and you stick with it but normally I use a bit of each method in a process that goes something like this:
First I use a long blade-scraper or filler knife and just go around and pull off any paint that is already loose and just waiting to fall off. This bit is rather fun….just like pulling sun-burnt skin of the back of you loved one (well I used to….not now of course).
Next I use a hot-air gun and a hook scraper (like a Skarsten or other tungsten bladed scraper) and try and pull off the majority of the paint. This is hard work, you burn your hands, your assistants hands, your tools (watch out for plastic handled scrapers….they melt) but as long as you don’t stop moving the gun about you won’t burn the wood. When eventually you get most of it off, it looks like you have almost got the job done, you have a pile of old paint. (you want to be a real nerd…..weigh the removed paint, it’s kinda interesting to know how much it all weighed. Now it looks like you have practically done it…..but in reality, although you have moved most of the paint….your work has hardly started.
OK, now you can use the Chemical Stripper, I have tried most but normally come back to using Nitromors, it seems a bit easier on the wood. I either use the Brown can if I am just stripping varnish, or the yellow can if I am stripping paint. The yellow can is not nearly so thick, so it runs a bit, but, it gets nicely into the cracks and seems to keep working a bit longer. (But hey, the Red and Green cans seem to work to). Stipper takes a while to get through the outer layer, but if you have already used a hot-air gun to take off the majority then getting the Nitromors to attach what is left should be easy. Even when you have already removed most of it….you will still find that you can easily use a ton more stripper just taking off the little niggly bits. If you want to start with the stipper and miss out on the hot-air gun then it can be worth abrading the surface first before you apply the stipper as this helps it get into the varnish. Stripper can work very nicely, but do not underestimate how much it will take. If you are going to use lots of stipper, it will certainly be worth choosing where you buy it from with care and also buying it in the gallon cans which, if you search around you can get for about 30-35 quid.
Once you have got all the varnish/paint off, you will still need to give it a good sand to clean it all up. By now the boat will look like you have already removed all the paint/varnish….but still have some marks’n’stuff. You are going to hate me to say this…..but in terms of time, you are now most probably only 60% of the way through the job. That sanding goes on and on and the bottom line is that the more you do, the easier it will be to varnish your boat and the better it will look when it is finished. It’s an old adage, but none the less true, that the better the preparation…..the better the finish