Sanding diggers casting resin

[timbertom]

Hi all,
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A quick question in regards to sanding ‘diggers casting and embedding resin’.
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I’ve filled a number of swirls, holes and features in a messmate tabletop that will be finished with Danish oil.
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I did the filling last night and plan to sand this evening.
-######### Is there anything I should consider before sanding?
-######### How difficult is it to sand?
-######### Can it be hand sanded or do I need to use a (smaller) belt sander? #(I was a bit generous with the application to allow for shrinkage – it was raised up to 2m out of the cracks)
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Ive read quite a few forums that have been helpful but would appreciate some specific instructions!
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Cheers, tom

[silentC]

I usually scrape it down level first using a card scraper before sanding. As it's fairly hard stuff, you'll probably find it takes awhile to sand down flush and there's the danger that you might sand a shallow groove around it in the timber. If you're going to sand it, make sure you use a sanding block.

I did use a belt sander once but I found the heat made the resin a bit sticky.

I'd probably be inclined to leave it a little bit longer though. It should be fully cured within 24 hours but I've found that it can still be a bit sticky even after a couple of days.

[timbertom]

Hey silentC, thanks for the response!

In regards to card scrapers, is there a particular type or size I should use? Forgive my ignorance! I've never used one before..!

Tom

[silentC]

I made mine out of an old hand saw blade. It's about 6" long and 3" wide. There's a bit of a knack to sharpening and using, but once you start using one, you'll find them very handy when working with hardwood.

There's plenty of threads on here about how to use one. Basically you use a hardened steel rod of some sort (screwdriver handle works) held at an angle of about 5 degrees off horizontal and run along both sides of each edge to turn a bur. Then you hold the scraper between your thumbs and fingers, tilt the top in the direction you're cutting, and push or pull the scraper. It should make a nice little pile of shavings. Practice on a bit of scrap before going near your table top though.

What you're doing will look great though. I like the natural voids and once you've applied the finish, the resin will look like water.

[timbertom]

Great.. Could I use a paint scraper or blade scraper? Seems anything with s sharp edge should be able to shave the resin down?

[silentC]

I wouldn't - there's a risk that you might damage the wood. A card scraper or cabinet scraper (basically the same thing but it's in a body that holds everything at the right angle etc) are the best tools for the job. They will give you a very smooth finish that is flush with the surrounding wood.

Don't be put off the card scraper, it all sounds a bit fiddly, but it's well worth the effort. If you don't want to make one, you can buy them from any woodworking supplier, along with the burnisher (which puts the bur on the edge) and one or the other will probably come with instructions on how to use them. Or plenty of people on here know all about them.

But if you just want to get the job done, you can certainly sand it, just be careful.

[timbertom]

So, just to update..

last night i thought id attempt it with a blade scraper picked up from the paint isle at bunnings.

it seems to work the same way you described a card scraper to work. i.e. shavings everywhere! however, it took a very long time!! is this task supposed to be this difficult or is it generally considered relatively easy and simple (if you have a card/cabinet scraper)?

the other difficulty i had was in areas where the fissure begins to level out with the top the resin would want to come away and a few times it did peel out. is this a common issue? I've refilled the few areas where this happened and aim to give it another go.

one last thing, in the example above, where the fissure beings to level out, its difficult to get the resin flush without it wanting to peel of the table ..?

thanks for your patience and responses..

cheers, tom.

[silentC]

Could be the blade scraper is not as sharp. It generally takes only a few minutes with a card scraper. Plus you have four re-sharpenable edges, so when it stops cutting well, you flip to another edge, and then re-sharpen when they're all dull.

With the very fine/shallow fissures, this is where you need a really sharp blade, because it tends to grab and pull it out rather than slicing it off. You also need to get a good bond in there and, although I've only done it this way once, it was recommended to me to paint some neat resin on thinly first before pouring the mixed resin and catalyst. That also helps with preventing air bubbles from forming.

I've often had to apply more resin after scraping to fix up things like that. But because you're working with a hard smooth material and a soft friable one, the edges are always going to be difficult to get perfect. I've found that once you get it to a point where your main voids are looking good, you can apply some sanding sealer which fills up the grain and any imperfections in the resin.

Another method I have used is to apply some clear Araldyte to the smaller cracks. It seems to stick better and looks the same once scraped and finished.