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alanganes
10-15-2014, 08:39 PM
So my youngest son is trying to make some sort of movie prop replica using fiberglass cloth and resin to make some of the parts. The parts will pretty much be flat panels. So we tried a test by just laying out a small section of the glass cloth (maybe 3" x 3"), mixing up some resin and hardener that I had around and brushing the resin in.

So after maybe 30 hours, it is mostly set up, but is still tacky. So the test was not an utter failure, but I'd like to know this will work before moving on to a more official effort.

I'm curious why this is still tacky. The stuff that was left in the mixing cup and the stuff on the brush set up solid (in a bit less time) and are far less tacky. I took care to mix well and in as close to the proportions the directions cite. It's a bit difficult to be too exact, but I don't recall this being super critical.

My main question is if the resin goes bad with age. The can of stuff I have is maybe 5 years old, though I got a new tube of hardener. The guy at the NAPA store, who I know and is an autobody guy from way back felt that if it was not gelled up thick, it was likely OK. Bit then he was not 100% on that because he uses it enough that his stuff does not really get old. Any other experience on that?

The stuff I am using is this:

NAPA Fiberglass resin kit (http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Fiberglass-Resin/_/R-BK_7651285_0361074355)

Any other thoughts on if I did something wrong? Should I just get new resin?

KJ1I
10-15-2014, 08:44 PM
Yes, resin goes bad with age. From the sound of your test, either there wasn't enough hardener in the mix, or one or both components has expired. From its age, I'd guess its past its use by date. Storage is greatly effected by storage conditions as well as just the age. I'd suggest doing another test using more hardener in the mix, if that doesn't work, get new resin.

Axkiker
10-15-2014, 08:55 PM
Ohhh wow I can tell you way more than you want to know about resins. I am just about finished rebuilding the stringers, floor and transom in a 23' boat. I had to basically learn from scratch.

Without knowing what kind of resin you used it could have very well been a non waxed resin. This type of resin is designed to either have wax added to the mix or PVA sprayed over the final layer. Sealing it from air is what causes it to cure and not be tacky. So if yours needed wax it will remain tacky for days if not weeks.

Axkiker
10-15-2014, 08:59 PM
Also, i have no idea how much glass work you intend on doing. If a lot, I highly suggest getting away from the local big box stores. I originally was using that type resin for some small tasks and I can tell you the stuff from the pros is way better. It is also way cheaper if you are in need of 1 gallon +. Not to mention they sell the glass which is also way cheaper if you need larger quantities.

I bought all my supplies from http://www.fiberglasssupplydepot.com/ They were great to work with and I received my materials within 3 days. I have no affiliation just a happy customer. There are also several other big online suppliers you could check im just not sure who.

alanganes
10-15-2014, 09:34 PM
Thanks for the quick replies.

I'm pretty sure I got enough hardener in it, but I'll try again as it costs nothing really to try. I'm guessing that you guys are right, the stuff is just too old.

This was made for small auto body repairs, so I don't think it requires any wax or anything like that. There is no mention of that in the instructions on the can anyhow.

I'm not doing all that much, maybe a few square feet total, if even that. So it likely won't make much sense to mail order a big batch, though the pricing "per pound" looks way cheaper. If this new stuff does not set up I'll just get a new can.

I appreciate you both sharing your expertise.

Juiceclone
10-15-2014, 11:00 PM
The simple answer is most resins are formulated to allow more layers to be applied. The surface will not fully cure in the presence of air.. This allows the next layer of cloth and resin to bond completely. The last layer is a different product, formulated with a little wax in the mix and that way air does not touch the outer surface, so the resin cures completely.... From experience, you can heat up some unmixed resin in a container in a pan of water on a stove, and add a little wax to it ...the heat will melt the wax, stir it up a little and you have your "finish" resin. I used a birthday candle for the wax in a quantity of about two cups resin ....worked perfectly.:cool:

CarlByrns
10-16-2014, 12:13 AM
You have polyester resin which has a shelf life. It should have set up very quickly- that's why its popular for autobody repair. It's also very cheap- a quart at any auto parts place will be about $8.

The hard part will be disposing of the old stuff :(

radkins
10-16-2014, 05:47 AM
The resin itself will last many years, I have been using some resin that was stored in a 1 qt glass jar over 15 years ago and it's still good, it's the HARDENER that goes bad! That stuff usually won't last more than a few weeks after opening the tube and even when unopened it won't last forever, I bought some (hardener) at a local ACE hardware a few months ago that obviously had been hanging on the rack for a long time judging by the condition of the package it was in and sure enough that one was bad. I later picked up another tube of the stuff at Wal-Mart, you can buy the hardener and resin separate, and that tube of hardener works just fine. The 15+ year old resin sets up just like it did all those years ago when I was still doing body work with the fresh hardener, old hardener is a well known problem in a body shop that does 'glass work.

Now after having said that it does not at all sound like an age related hardener (or resin although resin seems to last) problem but rather a temperature problem. This stuff needs to be really warm for it to set up properly, at much below 70 degs and it takes a long time and any colder than that it will not set properly at all! The fact it set up ok in the container is a very good indication the materials were still good and the mix was right. What was the temperature where the layup was located during the cure?

bob ward
10-16-2014, 06:54 AM
Assuming we are talking about polyester resin, yes it definitely has a shelf life. I used to buy 500kg or so a month and depending on the maker it had a 3 to 6 month shelf life. That's not to say it won't set when it is 2 or 4 years old it will just take longer and need more hardener. Should be fine for decorative purposes but no good for anything more serious.


MEKP hardener also has a shelf life, typically twice that of resin.

Re fibreglass kits from the big box stores, DON'T TOUCH THEM. I knew a guy who made up those kits. When he needed supplies he would go round the fibreglass wholesalers and do a deal on the grossly out of date drum of resin that had been forgotten in a corner. As long as it was still liquid and smelt like polyester resin that was fine by him.

Epoxy resins are a different kettle of fish, they have shelf lives measured in years.

radkins
10-16-2014, 07:08 AM
Temperature and old hardeners are BY FAR the biggest cause of fiberglass layup failure but everyone wants to blame the resin?????



Believe what you like about the common resins used in auto body work, Swiss and Bondo brands being the most common, but the resins will last MANY YEARS! As I just said I am currently using a resin (Swiss brand) that has been in a glass fruit jar for well over 15 years and back when I still had the shop we once used resin from a 5 gallon can that was also several years old, it had lost solvents to the point of being thicker and it still hardened just fine! HARDENER is another story however and has a rather short shelf life even when unopened but once opened it will last only a few weeks, almost any auto body worker who has done a lot of 'glass work will be well familiar with the old hardener problem! While I would agree that old resins may not be suitable for critical work I know for a FACT that old resin commonly sold for auto body repair will harden just fine even though it may not (or may!) reach full strength. Some resins may have a short shelf life but as well known as the common problems are, temperature and old hardeners, I am just astonished that they are not even mentioned.

Old material is not the problem here anyway, he said the darn stuff hardened just fine in the mixing cup, and it seems that it hardened somewhat in the layup but remained sticky, probably too late to save that layup but I am willing to bet that the next one will work just fine if it's kept warmer.

alanganes
10-16-2014, 07:31 AM
Interesting feedback.

These were just sitting in my shop, so the temp was probably low 70's F when I mixed and spread it. might have gone to mid 60's over night. The hardener I used was a tube that I had just purchased, but I have no way to know how long it was on the shelf.

Should I put these under a warm lamp or something to set up on the next try?

My recollection of using this stuff was as Carl mentioned, that it set up pretty quickly. It does advise to not mix more that you can use in 15 minutes. So as I was using this, I was questioning my memory of how fast it would start to get stiff in the cup. This batch stayed pretty fluid for a long time, maybe an hour of more, but I was not really keeping track.

This stuff is pretty cheap, I think I may just grab a new can at the part store tonight and try again. Nothing lost here as this was just some test parts.

Related question: The glass cloth comes in two styles. One looks like a regular woven fabric with the fibers regular and at 90 degrees to each other. The other is a mat type stuff that has what look to be random length fibers at random angles and is a bit thicker.
Will one set up more rigid than the other when the resin is applied to it?

There is no serious strength required here, just needs to be strong enough to support itself and not bend or break.

Thank you all again for the insights.

This is the exact resin I have, assuming it has not changed since I bought this stuff:

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Fiberglass-Resin/_/R-BK_7651285_0361074355

radkins
10-16-2014, 07:44 AM
Without a doubt temperature is the problem here! Yes you should apply some heat, a heat lamp or other heat source will in all probability solve your problem.


FWIW, the resin kit you link to is re-labeled "Bondo" brand, not exactly top-of-the-line stuff but quite alright for auto body and most non-critical applications but I certainly wouldn't use it for marine use.

rowbare
10-16-2014, 08:17 AM
The hard part will be disposing of the old stuff :(

That isn't so hard, just dump whatever hardener you have in the resin and mix. Once it hardens, even if it is sticky it is considered solid waste.

bob

Axkiker
10-16-2014, 09:27 AM
Without a doubt temperature is the problem here! Yes you should apply some heat, a heat lamp or other heat source will in all probability solve your problem.


FWIW, the resin kit you link to is re-labeled "Bondo" brand, not exactly top-of-the-line stuff but quite alright for auto body and most non-critical applications but I certainly wouldn't use it for marine use.

Out of curiosity why do you say this. I have always been told you needed at least 60* to lay resin and thats what I have gone by. I havent had any troubles but then again im using different resin.

Axkiker
10-16-2014, 09:31 AM
Re fibreglass kits from the big box stores, DON'T TOUCH THEM. I knew a guy who made up those kits. When he needed supplies he would go round the fibreglass wholesalers and do a deal on the grossly out of date drum of resin that had been forgotten in a corner. As long as it was still liquid and smelt like polyester resin that was fine by him.



I agree with this totally!!!! I have seen a BIG difference between what ive bought online and at the box stores.

You may try a different brand. I bought some labeled by elmers from Lowes and was able to use it on a smaller mold making project. Maybe give it a whirl this time.

Jay Fleming
10-16-2014, 09:37 AM
Try Solarez. From what I understand it is temperature independent, rather light reactive.

radkins
10-16-2014, 11:00 AM
Out of curiosity why do you say this. I have always been told you needed at least 60* to lay resin and thats what I have gone by. I havent had any troubles but then again im using different resin.

This stuff is really temperature sensitive, the resins sold for auto body and general use are very unreliable below 70 deg, at 60 deg (for these resins anyway) they will likely stay soft and tacky for excessively long periods of time. If it gets much below 60 deg it may not set up at all and if they sit uncured due to cold temperatures for too long they will never cure even if heat is applied later. During cold weather this was always a problem for us. Although we had IR heaters in the paint booth for primers and paint all the body work was done in the shop area that was heated with gas heaters, even with the shop comfortable it still would sometimes be chilly enough near that concrete floor to require heaters for curing 'glass resin and to a lesser extent "bondo" type plastic body fillers. The plastic body fillers also are polyester resins with talc and a few other ingredients added but cursorily enough they are much more cold tolerant than the liquid resin, which BTW is sometimes added to plastic body fillers as an old "shop trick" (doing this is called "body honey") to thin them for skimming and the added resin cures just fine with the paste hardener used for "Bondo".

kendall
10-16-2014, 11:17 AM
As mentioned, you have lay-up resin that doesn't fully cure in air. A n0-wax option is to cover the last layup with a sheet of plastic, If semi-cured apply a thin coat of resin, use a roller or squeegee to press the plastic sheet down and smooth it, then let it sit till cured. This also has the advantage of providing a very smooth surface. When cured the plastic will normally peel off easily. ridges from creases in plastic can be sanded smooth.

dian
10-16-2014, 12:49 PM
go and buy some epoxy.

radkins
10-16-2014, 02:09 PM
This stuff will cure out ok but it usually takes about 24 hours for the stickiness to go away, we always tried to do 'glass work on cars/trucks one day and let them sit overnight before sanding, if sanded while still sticky it made for a LOT of clogged paper before the uncured surface was removed but if left to the next day it was no problem. besides at the "sticky" stage it was still somewhat soft and couldn't be worked nearly as well as if it was given a full 24 hours. From what the OP has said and for what he is describing for the use all he really needs to do is use some heat (make sure the surface is about 70 deg or more not just the room temperature) and give it a full day and I truly believe his problem will go away. I know there are different resins out there meant for different purposes and they have different characteristics but the auto body type such as he linked to is something I have used a great deal of since 1971 and what he has described as his problem is extremely common with this stuff.

kendall
10-16-2014, 07:33 PM
go and buy some epoxy.

Epoxy is good, but expensive if you don't need the added strength.

bollie7
10-16-2014, 07:38 PM
That isn't so hard, just dump whatever hardener you have in the resin and mix. Once it hardens, even if it is sticky it is considered solid waste.

bob
Just a word of caution here. Polyester type resins are "exothermic". Meaning they generate heat when they are curing. In a situation like Bob has mentioned above, it would be very easy for the resin to catch fire. It would be safer to catalyzethe old resin and then pour it into a disposable aluminium oven tray or something like that to spread it out a bit. (to increase the surface area) Or sit the container of resin in a larger container of water.
After reading all the replies here I can't help noticing that no one has mentioned the safety considerations when working with polyesters (and other ) resins. The catalyst - MEKP (methyl ethyl ketone peroxide) is nasty stuff. Dont get it in your eyes. If you do theres a very good chance you will loose the sight in that eye. There are lots of other things to be aware of with it as well.
http://www.compositesaustralia.com.au/for-industry/health-and-safety/methyl-ethyl-ketone-peroxides/
In relation to the OP's problem, as others have said its probably due to the ambient temperature being too low. When I was doing a lot of glass repair work on my fibreglass car (http://www.bolwellcarclubnsw.com/page18.htm) I found a cheap fan heater worked really well. The fan distributes the heat more evenly over the area. You do need to have good ventilation in your work area as well.
regards
Bollie7

darryl
10-17-2014, 04:01 AM
My experience with polyester resin is that it will last a few years easily if not stored in the heat. Hardener not so much so.

An hour or more in the cup and it's still liquid- not enough hardener, or bad hardener.

Tacky surface- humidity has something to do with it, but so does resin type. Unwaxed resin normally does this. Just paint on a coating of waxed resin and let that set up. I buy unwaxed resin and just add the wax to a batch for the final layer. It is not recommended that you use waxed resin for multiple layers, as you can easily get poor bonding if the previous layer cures too much before the next layer goes on. It's pretty easy to have this happen.

I would not mix epoxy and polyester resins- supposedly you can epoxy over polyester, but not the other way around. If you're going to use one, stay with that. I've done layups in both resins, and usually only use epoxy if I'm going over styrofoam.

Cloth, matt, etc- matt has a binder which holds it together, while cloth doesn't. The binder needs polyester resin to soften it to allow the matt to conform to a mold or substrate. I'm not sure how well epoxy will dissolve the binder, but from what I've been told it's not recommended. My supplier doesn't carry the finest cloth, though it can be ordered in. If you need thin cloth- well, that's something you CAN find in consumer stores. Besides being weaker because of being thinner, I'm not sure that it would be inferior- glass cloth is just that, so what's going to be cheap about it? Use it where you need thin, use heavier cloth where you need more strength, use roving for highest strength. There is a select product that has more strands in one direction than the other for more strength in that direction. Then of course there are the other cloths- kevlar and carbon fiber. I've even used silk, but only because I had it and was willing to experiment. It worked fine.

I've mixed the odd batch 'hot', or fast, and run out of time to apply it. I've never had a batch catch on fire, but some have melted the container and some have smoked.

I've had my share of eff-ups. More than once I've been bitten by white glue- usually it's a build-up of plywood or whatever that is to be glassed over. If the resin softens and mixes with a glob of white glue before it's had time to set, you get a semi-permanent soft spot. More than once I've tried to get the fiberglass to form around too tight of a radius, and that's a mess. I've learned to use filler to round out corners, etc before glassing.

Fiberglass 101- $.02

alanganes
10-17-2014, 07:21 AM
Once again, thanks very much for all of the input.

Work has kept me from trying again yet, but will be doing that this weekend. I checked the original test parts and all are pretty much dry, one is just barely sticky to the touch. So it looks like I may either need more heat, more hardener or maybe both.

I think I'll try a bit more hardener and put them under a light bulb that will keep them warmed. We are doing this outside when it gets mixed up, but it is sitting in my shop to set up, temps there are likely hovering in the high 60's, so a lamp should add all the warmth I need. Going to try squeezing the sheet of plastic on top as suggested in several of your replies, just to cover all the bases.

I appreciate that all took the time to chime in.
Thanks again,

Al