andyscotland Posted October 31, 2019 Share Posted October 31, 2019 Ok, so I managed about 2/3 of my roof the other day and it went ok, consolidated the resin happily and it has set up nicely. Then we got hit by rain again and some got round the tarp and onto the boards in the section we've not done. By today I thought the boards were dry (~10% on my electronic meter, and did a condensation test with some clear plastic in the sunshine for an hour). As we laid the first piece of CSM it formed some big bubbles. The paddle roller moved them about and split them up but they kept coming back - i.e. they were forming within the laminate. Just could not get rid of them with brush, roller, extra resin, anything. My first assumption was that the boards were still wet. We stopped and packed up, as we did I noticed that the wasted resin in the bucket was very hot - 80 degrees in places on my IR thermometer. I'm now wondering if perhaps I'd put in too much catalyst, and that had caused the bubbling? I put in 4% as boards and air were fairly cold, but the resin had been inside so was warmer, maybe more like 15 or 16 degrees. The resin has cured with lots of tiny bubbles throughout (and some bigger ones) but no visible milky/white spots... Any of you GRP experts got an opinion? Meanwhile I have built a much more robust tent over the whole thing in the hope I can get it to dry out properly before we try again. Assuming I'll need to sand the bubbly bit right back to the wood, fortunately it's only about 1m2. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 31, 2019 Share Posted October 31, 2019 Catalysed resin will get very hot in a bucket, I've seen a bucket catch fire before now, just because of the exothermic reaction. My guess is that the bubbles were caused by moisture, possibly coming up from the substrate. May have been that the surface of the substrate was dry, but there was moisture trapped within it. The slightest hint of moisture can be a real bugger with polyester/vinylester layups. Over-catalysing resin that wasn't very cold may or may not have made this worse, @SteamyTea may know, as it's a fair time since I've used polyester/vinylester resin systems, pretty much everything I've done in the past twenty years or so has been with epoxy. Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 31, 2019 Share Posted October 31, 2019 @SteamyTea will be along in a minute he's Mr GRP ... he loves the stuff. Link to comment Share on other sites More sharing options...
andyscotland Posted October 31, 2019 Author Share Posted October 31, 2019 17 minutes ago, JSHarris said: Catalysed resin will get very hot in a bucket, I've seen a bucket catch fire before now, just because of the exothermic reaction. My guess is that the bubbles were caused by moisture, possibly coming up from the substrate. May have been that the surface of the substrate was dry, but there was moisture trapped within it. The slightest hint of moisture can be a real bugger with polyester/vinylester layups. Over-catalysing resin that wasn't very cold may or may not have made this worse, @SteamyTea may know, as it's a fair time since I've used polyester/vinylester resin systems, pretty much everything I've done in the past twenty years or so has been with epoxy. @JSHarris thanks - moisture was my guess too, was just hoping it might in fact be something easier to resolve.... 12 minutes ago, AnonymousBosch said: @SteamyTea will be along in a minute he's Mr GRP ... he loves the stuff. Good for him - at the moment I pretty much hate it... ? but that's me unfairly blaming the materials for my own failure to make enough progress on the roof earlier in the year when I'd planned to be doing it... The combination of the short days, low temps and unexpected rain are killing me - thoroughly despondent about it all just now.... ? I'm sure when I can eventually get it to dry out and finish it off it will be worth it. Link to comment Share on other sites More sharing options...
scottishjohn Posted October 31, 2019 Share Posted October 31, 2019 1 hour ago, andyscotland said: I put in 4% WOW that is a lot Link to comment Share on other sites More sharing options...
andyscotland Posted October 31, 2019 Author Share Posted October 31, 2019 14 minutes ago, scottishjohn said: WOW that is a lot Standard (per manufacturer's instructions) for when the boards/air are between 5 and I think 11°C. I'm just going off the ratios printed on the mixing bucket (but forgot to allow for the resin having been indoors overnight) Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 31, 2019 Share Posted October 31, 2019 Doesn't sound unreasonable for use in cold conditions, TBH. I've seen hotter mixes used before now, usually by people who just want to speed a job up and aren't too fussy about quality. If the resin was a bit warmer than the roof, I wonder if that may have had the effect of pulling moisture out? Not sure, TBH, but the GRP roofs I've done (years ago) were done during the summer, in dry weather, and the problem we had with one of them was stopping the resin curing too quickly. It was a matter of mixing it and immediately empting the bucket on the roof, spreading it out, to try and stop it warming up and curing too quickly. 1 Link to comment Share on other sites More sharing options...
Temp Posted October 31, 2019 Share Posted October 31, 2019 3 hours ago, andyscotland said: As we laid the first piece of CSM it formed some big bubbles. The paddle roller moved them about and split them up but they kept coming back - i.e. they were forming within the laminate Sometimes a brush with bristles cut short used in a hard stippling manner can help get bubbles out. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2019 Share Posted October 31, 2019 5 hours ago, andyscotland said: The paddle roller moved them about and split them up but they kept coming back - i.e. they were forming within the laminate. Just could not get rid of them with brush, roller, extra resin, anything. Any chance of some pictures. Were you laying up on the flat? Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 9 hours ago, SteamyTea said: Any chance of some pictures. Were you laying up on the flat? Not easily unfortunately, the affected area is in the middle of the roof and 1' below a tarp that took ages to float over it (and now raining). I could maybe try and wriggle under to get one, will see if that's possible later on. The roof is about 10° pitch, but we were on a "flat" section of it, not e.g. a trim/rooflight kerb. Is that what you meant? Link to comment Share on other sites More sharing options...
SteamyTea Posted November 1, 2019 Share Posted November 1, 2019 I don't think it was water, or over catalysing. Did you spill any resin on the mat that then set hard, before you started? This used to happen quite alot, a few spots of hardened mat does not want to play nicely. Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 3 minutes ago, SteamyTea said: I don't think it was water, or over catalysing. Did you spill any resin on the mat that then set hard, before you started? This used to happen quite alot, a few spots of hardened mat does not want to play nicely. Hmmm. Pretty sure we didn't, it was straight off the roll and didn't notice any, and that was the first batch we mixed of the day. Could it be that over catalysing meant the top started to skim over/set before we consolidated? Although the resin in bucket was still liquid... Link to comment Share on other sites More sharing options...
Ferdinand Posted November 1, 2019 Share Posted November 1, 2019 (edited) Not claiming to be very knowledgeable myself, however dad ran a grp business for 25 years and I was often around - know all about getting resin off school trousers ? . I think, as you say, it is a redo from the wood. As to drying it out, have you tried a dehumidifier under a small taped tarp tent? That may speed it up but also potentially make it dryer than ambient would allow to make rework easier. Need to watch for potential fire risk, maybe. After the fact on bubbles and really for future readers, I think I might try cutting a slit and working in from the sides with the grooved roller. Potentially would leaving a small area undone and going back as if doing a repair allow moisture to escape? F Edited November 1, 2019 by Ferdinand 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted November 1, 2019 Share Posted November 1, 2019 Was the roll of mat dead dry? 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 1, 2019 Share Posted November 1, 2019 As the resin set, all I can think of at the moment is that there was some sort of inclusion in there. Case of sand off and start again by the sounds of it. 19 minutes ago, JSHarris said: Was the roll of mat dead dry? From what Andy says, yes, as there was no milkiness, which is the usual giveaway. 1 Link to comment Share on other sites More sharing options...
scottishjohn Posted November 1, 2019 Share Posted November 1, 2019 (edited) a wild guess boarding was not painted with a thick enough layer of resin first before cloth applied- A layer of resin first allows you to roll the laminate into the resin and any air comes out of the top of the cloth ,then add more to top as required to get it totally wetted and compacted takes alot more rolling than most people think to very easy to use to waste resin just dumping it on the top weigh the cloth --then use same weight of resin .thats ideal amount of resin to use --less than you think -- ok add more to give a real glossy finish if you like ,but its not adding much strength to the job -just making it less flexible yes its easier to use more so you don,t have to roll so much --but not as good a layup Edited November 1, 2019 by scottishjohn 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 1, 2019 Share Posted November 1, 2019 Just had a thought, though won't affect the remedy. Where these bubbles where you joined/overlapped the original, successful, layup? Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 2 hours ago, Ferdinand said: Not claiming to be very knowledgeable myself, however dad ran a grp business for 25 years and I was often around - know all about getting resin off school trousers ? . Handily I was wearing my building trousers but I did manage to effectively laminate them to my knees ? 2 hours ago, Ferdinand said: I think, as you say, it is a redo from the wood. As to drying it out, have you tried a dehumidifier under a small taped tarp tent? That may speed it up but also potentially make it dryer than ambient would allow to make rework easier. Need to watch for potential fire risk, maybe. That's an interesting idea. How airtight do you think that tent would need to be - don't want to attempt to dehumidify the Central Belt of Scotland... Might be tricky to seal the edge that meets the house roof in particular. The other suggestion I've seen is radiant infrared heaters and ventilation, but they'd need a good bit of space below the tarp. I'm almost starting to wonder if I should actually get some scaff and polytunnel sheeting and build a full-size tent over the whole thing, then let it dry properly and do the laminating and topcoat inside the tent... It's looking less and less feasible to get enough time to do it in daylight / after the dew / before the rain... 2 hours ago, Ferdinand said: After the fact on bubbles and really for future readers, I think I might try cutting a slit and working in from the sides with the grooved roller. Potentially would leaving a small area undone and going back as if doing a repair allow moisture to escape? Yes, that might have worked - good thought for next time... Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 2 hours ago, JSHarris said: Was the roll of mat dead dry? Yes, I think so. It had been in the building site downstairs so I suppose a chance it had picked up some airborne humidity? But no exposure to actual water. Link to comment Share on other sites More sharing options...
Ferdinand Posted November 1, 2019 Share Posted November 1, 2019 (edited) Reflecting, fan heaters might be an idea, as they would exclude incoming draughts. I think it would need a good seal - I was thinking a tarp with no holes (Which might not be a tarp) and an effective gaffer tape seal. Also depends on the power of your dehumidifier. You could stick a heater in there. If you had a scaffold tent you would need a bigger DH but the seal could be less good due to the increased volume. A fan heater in there would also really help, as DHs work better at higher temperatures - ideally 25-30C. You can also use something as simple as a hair dryer depending on the circs and the scale, perhaps in combination with someone holding a gold umbrella. Edited November 1, 2019 by Ferdinand 1 Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 2 hours ago, SteamyTea said: As the resin set, all I can think of at the moment is that there was some sort of inclusion in there. Case of sand off and start again by the sounds of it. From what Andy says, yes, as there was no milkiness, which is the usual giveaway. Managed to crawl in and get some pics @SteamyTea The bubbles were all transparent yesterday, some still are but some do now look more opaque. But not as white/milky as I saw on the resin that definitely did get contaminated with rain (now sanded off) earlier in the build. You can see on one of them how the mat was just pulling with the paddle roller rather than pushing down. Link to comment Share on other sites More sharing options...
andyscotland Posted November 1, 2019 Author Share Posted November 1, 2019 2 hours ago, scottishjohn said: a wild guess boarding was not painted with a thick enough layer of resin first before cloth applied- A layer of resin first allows you to roll the laminate into the resin and any air comes out of the top of the cloth ,then add more to top as required to get it totally wetted and compacted Actually that's possible - we were rushing a bit more than we should have been and maybe didn't wet the deck as much as we had previously. Would maybe also explain why the mat seemed to pull away from the deck in places as we rolled it? 2 hours ago, scottishjohn said: takes alot more rolling than most people think to very easy to use to waste resin just dumping it on the top weigh the cloth --then use same weight of resin .thats ideal amount of resin to use --less than you think -- ok add more to give a real glossy finish if you like ,but its not adding much strength to the job -just making it less flexible yes its easier to use more so you don,t have to roll so much --but not as good a layup Have one of the fancy cure-it buckets marked with a square metres scale, been fairly careful about measuring/estimating the size of each area and keeping an eye on the bucket to make sure we're using roughly the right amount. 2 hours ago, SteamyTea said: Just had a thought, though won't affect the remedy. Where these bubbles where you joined/overlapped the original, successful, layup? Small bubbles at the overlap (and throughout) but the big ones all in the centre of the area. 2 minutes ago, Ferdinand said: I think it would need a good seal - I was thinking a tarp with no holes (Which might not be a tarp) and an effective gaffer tape seal. Also depends on the power of your dehumidifier. Reflecting, fan heaters might be an idea, as they would exclude incoming draughts. Thanks - yes I think good seal will be tricky to achieve at the edges. The tarp at the top edge needs to extend over the house roof (otherwise any drip will fall onto the new OSB deck) but that would mean trying to seal to slates.... Had a fan heater up there under the tarp for about 36 hours before we started work yesterday and that did seem to be helping. Maybe I was just too keen to try again and had only dried the surface and should have waited longer to get moisture out from lower down... Link to comment Share on other sites More sharing options...
Jeremy Harris Posted November 1, 2019 Share Posted November 1, 2019 Looks like air bubbles to me. Also looks as if the resin was sticky, perhaps curing too quickly, and was sticking to the roller, which then pulled the mat up, creating the air bubbles. Link to comment Share on other sites More sharing options...
SteamyTea Posted November 1, 2019 Share Posted November 1, 2019 Does look like a combination of lack of pre wetting and then curing too soon. Like the Curates Egg. It is good in parts. Try a bit less hardener, and half the amount in the bucket. If we were doing a large job, then we incrementally increased the hardener as we went along. So say 2.5%, then 3% and then 3.5%. just make sure each layer is from the same batch. Actually I never worked in percent, we used the tradition mixed units if cc to the lb. Link to comment Share on other sites More sharing options...
SteamyTea Posted November 1, 2019 Share Posted November 1, 2019 (edited) For this sort of job you need to be resin rich. The excess resin should be drawn to the surface by the rolling. Don't press too hard on the roller, that can just pucker up the mat. The binder in the mat may take a minute or 3 to breakdown, so don't start rolling as soon as you have put the resin on, that just makes a mess and a noise. Edited November 1, 2019 by SteamyTea Link to comment Share on other sites More sharing options...
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