This is what's currently being tested:
Glue / Sealer
Extramite / Varnish
Extramite / Epoxy
Extramite / 2K HS Primer
Epoxy / Varnish
Epoxy / Epoxy
Epoxy / 2K HS Primer
PVA / Epoxy
PVA / 2K HS Primer *
PVA / Varnish *
* Discarded before painting, due to obvious sinking glue lines
Glue / Sealer
Extramite / Varnish
Extramite / Epoxy
Extramite / 2K HS Primer
Epoxy / Varnish
Epoxy / Epoxy
Epoxy / 2K HS Primer
PVA / Epoxy
PVA / 2K HS Primer *
PVA / Varnish *
* Discarded before painting, due to obvious sinking glue lines
Thanks. As you can probably imagine I'm hoping the Extramite ones do well, particularly the paint primered one. As that will be most likely my method.
Have you heard about a product called Valchromat. This is brightly coloured MDF that comes in a range of thicknesses starting at 8mm up to 30mm. It can be machined routed etc and the machined surface looks as good apparently as the original surface. Comes in 8 different colours I think. Made by mixing organic dye in the manufacturing process.
It might make the headache of painting the MDF go away.
It might make the headache of painting the MDF go away.
SteveT2 said:
Hi Steve
I've seen that stuff around my one local timber merchants. At first glance it doesn't look like a type of fibre board and feels a little like plastic or pot. I did have a brief gander but was scared off by the fact it was obviously treated and I wondered if it would react with the paint I use. I've thought nothing else of it until you just mentioned it, I also didn't realise that it kept a smooth(er?) surface after machining though it would seem a little obvious now looking back.
Just one thing to mention - its fairly expensive, much more than MDF if I remember correctly.
Actually with further inspection this looks promising, especially the part of moisture resistance:
http://www.avonplywood.co.uk/noframes/valchromat info.htm
I'll have to put that on the 'to try' list.
http://www.avonplywood.co.uk/noframes/valchromat info.htm
I'll have to put that on the 'to try' list.
I've seen coloured MDF being used by a US company that cuts textures into large sheets - think ripples and waves. I believe they're used in architectural applications. Can't find a link at the moment, but they're pretty impressive.
If it'd take a clearcoat without furring then it could look quite interesting when used for a speaker cabinet.
BTW I've not done anything with the blocks that were painted last week, and won't have time this weekend. I have however made a couple of new test pieces, which were glued with Cascamite, left for a week, and this evening one received two coats of poly varnish, the other two coats of G4 sealer. Will post when I have more to tell...
If it'd take a clearcoat without furring then it could look quite interesting when used for a speaker cabinet.
BTW I've not done anything with the blocks that were painted last week, and won't have time this weekend. I have however made a couple of new test pieces, which were glued with Cascamite, left for a week, and this evening one received two coats of poly varnish, the other two coats of G4 sealer. Will post when I have more to tell...
Spotted another couple of products that might be similar in effect to the Bonda stuff you showed me. Both are water clean-up which is nice.
Might be able to get this from my local hardware shop:
This is available from Axminster:
Might be able to get this from my local hardware shop:
An externally hosted image should be here but it was not working when we last tested it.
This is available from Axminster:
An externally hosted image should be here but it was not working when we last tested it.
Hi Rich,
I was considering the Rustins product, but as John pointed out (earlier in this thread I think) water + MDF is always a bad combination. My experience would reflect this - with International MDF primer anyway.
I've been trying to do the next set of test pieces (spraying on Urethane paint) for weeks now. Unfortunately, lack of time, and the lovely* weather we've been having in the UK recently has made it impossible.
I did total up the cost for another shed + explosion proof fan + 7CFM free air capable compressor + air fed mask so I could spray indoors. Once I regained conciousness, I put the figures in the bin...
* For the non-English, this a subtle way of saying - f*&! me it's been p*ssing it down for weeks, everything's wetter than an otter's pocket, when the h*ll is it going to stop.
I was considering the Rustins product, but as John pointed out (earlier in this thread I think) water + MDF is always a bad combination. My experience would reflect this - with International MDF primer anyway.
I've been trying to do the next set of test pieces (spraying on Urethane paint) for weeks now. Unfortunately, lack of time, and the lovely* weather we've been having in the UK recently has made it impossible.
I did total up the cost for another shed + explosion proof fan + 7CFM free air capable compressor + air fed mask so I could spray indoors. Once I regained conciousness, I put the figures in the bin...
* For the non-English, this a subtle way of saying - f*&! me it's been p*ssing it down for weeks, everything's wetter than an otter's pocket, when the h*ll is it going to stop.
I know it goes against others judgement, but I'm not convinced a water based finish is the root of problems. The glue is water based. Any finish that goes on will either be solvent or water based either of which will have similar effect. Once things have dried it should all be the same 😕
If you can get me one stack of your blocks I'll get some of one of those water based sealers and see what happens. I'll pay for p&p or you can bring it to the meet.
If you can get me one stack of your blocks I'll get some of one of those water based sealers and see what happens. I'll pay for p&p or you can bring it to the meet.
Sploo - You spary outside? And you don't get bits of nature in your paint? For my last bit of painting (amateurish spray cans) I got some PVD pipes to make up a frame, covered it with plastic tarp and duct tape, and vented it with a 20" box fan and furnace filter. Hadn't considered an explosion-proof fan - hope I don't blow myself up. 
I picked up the idea from a book about setting up an auto shop in your garage. So after I took it back down I noticed a little touch up needed, so I sprayed in my back yard, and when it had dried - sure enough - there were some fluffy white fibers in it from some plant or another... 
I picked up the idea from a book about setting up an auto shop in your garage. So after I took it back down I noticed a little touch up needed, so I sprayed in my back yard, and when it had dried - sure enough - there were some fluffy white fibers in it from some plant or another... richie00boy said:
I guess what's really required is a coating that completely prevents any moisture transmission - if the moisture level doesn't change, then the MDF shouldn't move. I could be wrong, but I'd expect most of the water based primers won't protect as well as a damp proof sealer.
Some of the latest blocks I was making are stacked rectangles (I was going mad sanding all those curved edges). You could therefore just cut some squares, glue them with Cascamite, leave them somewhere dry for a couple of weeks, then coat with the water based sealer.
AdamThorne said:
Nowhere else to do it - the garage is full of power tools!
I had considered making a frame, mainly to reduce the number of flying things landing on what I'm spraying. The problem of course is that won't help when gallons of water are falling from the sky. This happens a lot during the rainy season here (usually from 1 Jan to 31 Dec 😉 )
If you were using cans, you'd probably be OK (ratio of paint to air being fairly low), but I'd still be careful - the stuff is still flammable. Plus in an enclosed space you really would want air fed gear.
My problem was getting the edges like yours - I don't have a router table 😉
The stuff is advertised as a sealer as well as a primer, I might give it a go anyway. I'll have a look on Axminster to see if I can get a big flush trimmer.
The stuff is advertised as a sealer as well as a primer, I might give it a go anyway. I'll have a look on Axminster to see if I can get a big flush trimmer.
Actually, the edges were done using a powered sander - I glue the blocks together, then sand them flush using a coarse grit paper (60 to 80).
I then follow it with a finer grit (120). You don't usually need to go any finer than that for MDF edges. I usually sand primer coats with 400 grit.
You've reminded me - I really do need to get round to registering for the meet... busy busy busy
I then follow it with a finer grit (120). You don't usually need to go any finer than that for MDF edges. I usually sand primer coats with 400 grit.
You've reminded me - I really do need to get round to registering for the meet... busy busy busy
Right... some progress to report...
I've not done anything with the set of test blocks I'd painted with black cellulose paint (the ones glued and sealed with numerous products). The Cascamite glued, poly varnish sealed block still shows some obvious lines, and the others are in various states - some lines visible, some look OK.
I'd made a set of three more blocks, all glued with Cascamite, clamped with lots of pressure whilst setting. One was coated in more varnish, one using Bonda G4 (a damp proof sealer I've recently bought) and one was raw MDF.
I sprayed all with several (approx 10) coats of white Urethane paint, as recommended by John.
The urethane is very different to spraying celly - the first couple of coats don't appear to do anything (looking like you'd spilt milk over the blocks), and then it builds up almost like plastic. As it sets it goes like warm chewing gum (I had a 'poke around' with some of the overspray).
It's been a few days since they were sprayed, and the surface has set, but they're all still very soft. So soft in fact, I'm not sure it's going to set. It did say 5-6days for through dry on the app sheet, so we'll see.
Impressively, it does indeed coat raw MDF (as claimed by John) - try doing that with cellulose! It's got some grain showing through, so it would need sanding and another few paint coats, but that's no different to using a sealer before painting.
Given the softness, and the thickness of paint, no movement is going to show through on any of the blocks for the time being, so I'll have to leave it and hope it sets.
I do have a feeling I might need to consider buying the 2K version. Anyone want to sell me a 10cfm compressor for 50quid so I can run an airfed mask. 🙂
I've not done anything with the set of test blocks I'd painted with black cellulose paint (the ones glued and sealed with numerous products). The Cascamite glued, poly varnish sealed block still shows some obvious lines, and the others are in various states - some lines visible, some look OK.
I'd made a set of three more blocks, all glued with Cascamite, clamped with lots of pressure whilst setting. One was coated in more varnish, one using Bonda G4 (a damp proof sealer I've recently bought) and one was raw MDF.
I sprayed all with several (approx 10) coats of white Urethane paint, as recommended by John.
The urethane is very different to spraying celly - the first couple of coats don't appear to do anything (looking like you'd spilt milk over the blocks), and then it builds up almost like plastic. As it sets it goes like warm chewing gum (I had a 'poke around' with some of the overspray).
It's been a few days since they were sprayed, and the surface has set, but they're all still very soft. So soft in fact, I'm not sure it's going to set. It did say 5-6days for through dry on the app sheet, so we'll see.
Impressively, it does indeed coat raw MDF (as claimed by John) - try doing that with cellulose! It's got some grain showing through, so it would need sanding and another few paint coats, but that's no different to using a sealer before painting.
Given the softness, and the thickness of paint, no movement is going to show through on any of the blocks for the time being, so I'll have to leave it and hope it sets.
I do have a feeling I might need to consider buying the 2K version. Anyone want to sell me a 10cfm compressor for 50quid so I can run an airfed mask. 🙂
Good update. I'm not overly excited by these results though. Having a finish that takes so long to set is just too risky for getting marks in IMO.
I should order some of the waterbased sealer I mentioned and crack on with that. I should have some offcuts in the loft I can use.
I should order some of the waterbased sealer I mentioned and crack on with that. I should have some offcuts in the loft I can use.
Good stuff sploo. Fingers crossed on the urethane.
For 2k you might want to consider one of the oil-less continuous run compressors. They're cheap and I've seen them used for such a task. The main advantage is you don't need a coalescing filter to get rid of the oil and water, one disadvantages is that after about 30 minutes of use they tend to heat the air passing to the mask so you end up breathing warm air.
I also saw a full airfed on ebay a couple of weeks ago that had an integral pump attached to the end of the air line. Think it was about £150.
Personally I'd avoid 2k though, you need good equipment and facilities to use it safely. I've had a nasty scare with it that saw me in at the doctors. Its deadly stuff.
For 2k you might want to consider one of the oil-less continuous run compressors. They're cheap and I've seen them used for such a task. The main advantage is you don't need a coalescing filter to get rid of the oil and water, one disadvantages is that after about 30 minutes of use they tend to heat the air passing to the mask so you end up breathing warm air.
I also saw a full airfed on ebay a couple of weeks ago that had an integral pump attached to the end of the air line. Think it was about £150.
Personally I'd avoid 2k though, you need good equipment and facilities to use it safely. I've had a nasty scare with it that saw me in at the doctors. Its deadly stuff.
Well, you could use Glatex 8, comes in clear as well as a number of solid colours... very durable, gloss finish, almost like plastic.
richie00boy said:
Careful handling greatly reduces the chance of marking whilst a product is setting, but if it never really sets then it's inevitable.
The single pack U-Pol clearcoat I've used gives a really nice finish, but it never sets hard - you can easily mark it with a fingernail, even weeks after. It doesn't require any mixing - straight from can to spray gun, so it's not like I'm getting a ratio wrong.
ShinOBIWAN said:
I know precisely zero about compressors (other than if you're after more than 6cfm it starts to get pricey - i.e. more than 300GBP). Could you give me some examples/links of what you mean by those units?
To be honest, 30 mins of use would be fine for me. Even if I were spraying a couple of large speakers, you're only running the gun (a HVLP turbine unit) for a few minutes, then waiting 10-15 for the flash off time. Hence I'd never run a compressor fed mask for more than a few minutes at a time.
2k is indeed nasty stuff. I always spray (everything) outdoors, and I must admit to having used 2k without air fed gear. Spraying small items + having reasonable lung capacity means you can take a deep breath, spray, walk away, switch off the turbine, then take another breath - what you don't breath surely can't kill you... (oh, I do cover all exposed skin when using 2k too - goggles, hat, gloves etc.)
Nordic said:
Couldn't find much, other than a couple of other forum posts mentioning it, with a quick google search. Could you post any more info?
sploo said:
Hi Sploo,
Yes, it takes forever to dry, so be patient. 🙂
How quickly did you spray the coats? A longer "flash" between coats can quicken drying time. The curing process is by oxygen absorpsion from the air, so a fan blowing on the blocks will speed the hardening time up.
A 2K version would be the ultimate, hard and ready to sand in a couple days, but for me, not worth the extra hassle.
MJL21193 said:
I was doing other stuff in between spraying each coat, so it varied between 20 and 30 mins. The datasheet didn't give any info on flash off time unfortunately.
Ironically, it was the first day in weeks that wasn't raining, but the conditions were a bit more windy than I'd usually spray in. Hence it got quite a bit of extra oxygen (and a few files)!
I'm getting very tempted by a compressor and an air fed mask, as I'd love the freedom to spray 2K paints. Plus it would allow me to get a small(ish) shed and spray even if the weather's not great - something I wouldn't do (spray in an enclosed location) without breathing gear.
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