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Bubbels or dust - how to proceed?
Hi Dan,
Thank you for a great online course. Over learned a lot.
Right now I’m in process of getting ready for spring and have taken some mahogni that has been varnished 2 times earlier. Removed scratches and flattened it as you described. So a good varnish foundation as base.
I’m in the build up phase and is expecting to polish the final layer as dust control is difficult.
Cleaned with tack cloth, thinner, tack cloth and then rolled Epiphanes 2k clear on (high wear) yesterday. No tipping. This morning it looks not quite as I hoped.
What’s the best way to proceed? (Sand back the bubbles/grain per build more on top as-is)
This morning it looked like this.
I did a light 320 sanding on the 3rd picture
Br Anders
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Hi Anders
This is a great example of the bubbles vs dust issue that so many people face. I would be 95% sure that what you have there is a dust issue in some way. There is a quick test that you can do to confirm this:
Roll, or brush (whatever you are using) some varnish out on a sample board, piece of scrap or other small item from the boat if you are varnishing that at the same time. Ideally not bare wood, something that is at a similar finish state to your boat if you have something, even if its previously painted thats fine, key it up as you would varnish. This is just because you don't want to do this test on an absorbent piece of fresh wood as it will effect your result.
Do this in the exact same environment as you are working on your boat in. When applying the varnish to your sample, actively try to induce as many bubbles in the surface as you can, as I do in Module 2 Lesson 1: https://danleeboatbuilding.co.uk/courses/varnishing-course-10-day-yacht-varnisher/lesson/module-2-lesson-1-my-top-5-traditional-varnishes/ foam rollers or brushes are good for this.
Watch the surface over the next few minutes, maybe up to an hour, but I would highly expect that all bubbles will have gone within this time. If you still see what you have above after an hour try popping it with a pin to see if it genuinely is a bubble. I don't think it will be.
If you can confirm that these aren't bubbles, we know you have a dust contamination issue and then we can start tracking down the source of that dust. I would recommend going through all of the recommendations in Module 7 Lesson 2 on Dust control and setup day. Be very thorough with using a clean roller or brush, sheet out your workspace, particularly overhead and compare the results of your next coat.
Let us know how you get on!
After you sand back and vacuum the dust are there voids in the center of each lump? I would think if they were bubbles the voids would be apparent after they were sanded open.
Quote from Dan Lee on 21st January 2023, 11:50 amHi Anders
This is a great example of the bubbles vs dust issue that so many people face. I would be 95% sure that what you have there is a dust issue in some way. There is a quick test that you can do to confirm this:
Roll, or brush (whatever you are using) some varnish out on a sample board, piece of scrap or other small item from the boat if you are varnishing that at the same time. Ideally not bare wood, something that is at a similar finish state to your boat if you have something, even if its previously painted thats fine, key it up as you would varnish. This is just because you don’t want to do this test on an absorbent piece of fresh wood as it will effect your result.
Do this in the exact same environment as you are working on your boat in. When applying the varnish to your sample, actively try to induce as many bubbles in the surface as you can, as I do in Module 2 Lesson 1: https://danleeboatbuilding.co.uk/courses/varnishing-course-10-day-yacht-varnisher/lesson/module-2-lesson-1-my-top-5-traditional-varnishes/ foam rollers or brushes are good for this.
Watch the surface over the next few minutes, maybe up to an hour, but I would highly expect that all bubbles will have gone within this time. If you still see what you have above after an hour try popping it with a pin to see if it genuinely is a bubble. I don’t think it will be.
If you can confirm that these aren’t bubbles, we know you have a dust contamination issue and then we can start tracking down the source of that dust. I would recommend going through all of the recommendations in Module 7 Lesson 2 on Dust control and setup day. Be very thorough with using a clean roller or brush, sheet out your workspace, particularly overhead and compare the results of your next coat.
Let us know how you get on!
Hi Dan,
Sanded back. I think the issue was too little varnish. Hopefully next layer will change everything 😆