32 replies to this topic

[bigtonyicu]

Hi Everyone,

In Canada (everywhere except the west) it is very hard to find HPDE pipe to make mortars with, I've found a local supplier that has been providing me with cardboard mortars (36" long with a 3" ID, 5/8" wall; cut in half make a great mortar) for a little while now and want to protect them as much as possible. I found this link on www.pyropage.com that talks about protecting cardboard mortars.

The exact sub section is currently down but this is what it says:

Treating Cardboard Mortars


One of the problems faced by pyrotechnicians is getting a reasonable life span out of their cardboard mortars. Myke Stanbridge documented this treatment which he claims will make cardboard tubes last 25 years or more. I'll report back in 2022 on whether it worked that well for me!

Perhaps the cheapest, easiest and most effective treatment for paper mortar tubes is the following:

• <LI class=MsoNormal style="MARGIN: 0cm 0cm 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt">Clean out any debris, cobwebs, etc. Use PVA adhesive to stick down any 'flapping' edges. <LI class=MsoNormal style="MARGIN: 0cm 0cm 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt">Rinse each tube internally with a strong solution of calcium chloride in water. Allow your tubes to stand until they are just damp. Calcium chloride is rather hygroscopic and will not dry past remaining damp. <LI class=MsoNormal style="MARGIN: 0cm 0cm 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt">Using a 25% w/w solution of sodium silicate in water rinse each tube internally. Pour out the excess into your bucket and let the tubes dry open end up. There is a chemical reaction that produces tough insoluble calcium silicate in the structure of the paper. This hardens and binds the surface making it resistant to damage by abrasion and alkaline residues. When dried give the tube a fresh water rinse to remove residual sodium chloride produced in the reaction and let dry open end up in a warm location.
• Coat your tubes externally with a mixture of spirits of turpentine 1 part (pine spirit NOT mineral turps) and boiled linseed oil 3 parts. Add 15% lampblack to the mixture if you want black tubes. Leave the tubes to dry for about two weeks, open end up... Omit this step if the tubes are for immediate use or will form elements of a boxed mortar block...

Note: I'm still using tubes prepared like this around 25 years ago, and they still function perfectly! The method of treatment is very quick and cheap once you've got set up... You can treat a hundred tubes in an hour or so for around 10 cents per tube. Painting costs around a dollar per tube and is not as effective... Regards, Myke.

Has anyone done anything like that before?

I'm just having a hard time finding calcium chloride, someone told me to contact a pool chemical supplier, apparently it's used for treating water for in ground pools as a water hardener.

any thought or other treatment Idea would be greatly appreciated.

[pyromaniac303]

Calcium chloride is used in moisture traps, your local hardware store should sell it in refill bags for them. It is usually in large flat flakes, but is easily crushed.

[bigtonyicu]

Calcium chloride is used in moisture traps, your local hardware store should sell it in refill bags for them. It is usually in large flat flakes, but is easily crushed.

moisture traps??? desicants? I thought those used silica gel

[pyromaniac303]

The brand I bought (Kilrock) uses calcium chloride, approx 98% pure. Its so hygroscopic that it just sucks the moisture out the air, and best of all its cheap. It comes in handy for rapidly drying stars too.

[bigtonyicu]

ok... I want to move to England... all the desiccant here are silica gel, and reletively expensive. but the local pool supply doesn't have it in stock but they can get it and it's reletively cheap so he's going to order some in for me. Have you tried to treat tube like this pyromaniac303?

[Arthur Brown]

This is something I have heard good thing of! But never done myself.

Can any of the USA rack and mortar suppliers send HDPE or GRP tubes or complete racks across the border to you? Typical UK GRP mortars have a one piece construction with integral base. HDPE usually get a wooden plug pinned and glued in

[pyromaniac303]

I have a free supply of 2" and 3" cardboard mortars from work so never really had the need to protect them. The other tubes I have are GRP, and they are excellent quality.

[digger]

Here you go I have tidied the text up a bit for you as it is a little difficult to read with all that HTML in there

Perhaps the cheapest, easiest and most effective treatment for paper mortar tubes is the following:


1) Clean out any debris, cobwebs, etc. Use PVA adhesive to stick down any 'flapping' edges.

2) Rinse each tube internally with a strong solution of calcium chloride in water. Allow your tubes to stand until they are just damp. Calcium chloride is rather hygroscopic and will not dry past remaining damp.

3) Using a 25% w/w solution of sodium silicate in water rinse each tube internally. Pour out the excess into your bucket and let the tubes dry open end up. There is a chemical reaction that produces tough insoluble calcium silicate in the structure of the paper. This hardens and binds the surface making it resistant to damage by abrasion and alkaline residues. When dried give the tube a fresh water rinse to remove residual sodium chloride produced in the reaction and let dry open end up in a warm location.

4) Coat your tubes externally with a mixture of spirits of turpentine 1 part (pine spirit NOT mineral turps) and boiled linseed oil 3 parts. Add 15% lampblack to the mixture if you want black tubes. Leave the tubes to dry for about two weeks, open end up... Omit this step if the tubes are for immediate use or will form elements of a boxed mortar block...


Note: I'm still using tubes prepared like this around 25 years ago, and they still function perfectly! The method of treatment is very quick and cheap once you've got set up... You can treat a hundred tubes in an hour or so for around 10 cents per tube. Painting costs around a dollar per tube and is not as effective... Regards, Myke.

Edited by digger, 29 July 2008 - 11:15 AM.

[pyrotrev]

I tried this many years ago, and found a serious problem - not all the the CaCl2 that soaks into the cardboard reacts with the silicate, leaving a hygroscopic layer under the calcium silicate surface which becomes damp with heating. With substantial shells the heat of the lift charge boils this moisture, causing bubbling of the inner surface of the tube and possible shell jamming/flowerpotting. It might be worth trying it with soaking in silicate first then rinsing with conc. CaCl2 solution, alternatively I'm sure there's some resins that would do a good job.

[digger]

I tried this many years ago, and found a serious problem - not all the the CaCl2 that soaks into the cardboard reacts with the silicate, leaving a hygroscopic layer under the calcium silicate surface which becomes damp with heating. With substantial shells the heat of the lift charge boils this moisture, causing bubbling of the inner surface of the tube and possible shell jamming/flowerpotting. It might be worth trying it with soaking in silicate first then rinsing with conc. CaCl2 solution, alternatively I'm sure there's some resins that would do a good job.

Do you know of any suitable resins for this procedure?

[bigtonyicu]

Here you go I have tidied the text up a bit for you as it is a little difficult to read with all that HTML in there

Thank you very much, I had fixed the beginning of it but didn't catch the ones that were in the text.

Do you know of any suitable resins for this procedure?

Well I can think of a few High temp or structural Epoxy that should do nicely but would be a pain to get in them coated in there (so thick). Epoxy made to coat floors get very runny when warm, might be worth a try. Fill a tube (or a 5 gallon pail then dunk quickly and hang dry. the coating should be really thin (as long at the epoxy is warm enough) so it shouldn't be a problem with shrinking the ID. but it will singe over time.

Other option is polyester, Fumes are nasty!!! But they do make a top coating product that tends to be very runny and they will withstand higher temperatures then room cured epoxies. The catch (other then the fumes) is that they harden by catalytic polymerization (like epoxy adhesives) you add MEKP (Methyl Ethyl Ketone Peroxide) once mixed you can not stop the reaction the rate of reaction is determined by the amount of MEKP (less = slower) you have to use all of it, no putting a lid on it and coming back to it later.

I do think that the Sodium silicate to Calcium silicate is a better option the catch is how to get the residual water out from the cardboard. I do like your Idea of soaking the tube in sodium silicate and then letting them dry fully before reacting with calcium chloride. I wonder if there's another calcium salt that would be suitable.

Edited by bigtonyicu, 29 July 2008 - 03:27 PM.

[digger]

I do think that the Sodium silicate to Calcium silicate is a better option the catch is how to get the residual water out from the cardboard. I do like your Idea of soaking the tube in sodium silicate and then letting them dry fully before reacting with calcium chloride. I wonder if there's another calcium salt that would be suitable.

Does it have to be calcium? there are plenty of insoluble silicates formed by this same reaction.

I have had a look at polyester resins, there are even intumescent resins. The question is do these swell on the application of heat.

[bigtonyicu]

Does it have to be calcium? there are plenty of insoluble silicates formed by this same reaction.

I have had a look at polyester resins, there are even intumescent resins. The question is do these swell on the application of heat.

It doesn't have to be calcium most silicate will work I just want to get away from the calcium chloride because of its hydroscopic nature. Ideally it would be any other chemical that is cheap and in a perfect world would be soluble in alcohol, and what ever silicate created wouldn't be soluble in alcohol (I don't think any of them are but just being safe). That way we could coat the tube in Sodium silicate, let them fully dry, then coat with the alcohol and "something" blend; and it would result in a tube that contains no moisture and a silicate coating.

Bottom line, insoluble silicates are the best coating; they resist high temp and protect the tubes from rain. But theoretically any low viscosity, high temperature stable, none water soluble coating will work.


I wonder it calcium silicate has any solvents that way in a single step is could be applied and let to dry and we’d be in business

[bigtonyicu]

Can any of the USA rack and mortar suppliers send HDPE or GRP tubes or complete racks across the border to you? Typical UK GRP mortars have a one piece construction with integral base. HDPE usually get a wooden plug pinned and glued in

That would bring some unwated attention, now a days why raise flags in you don't have to lol

[Shake]

what is the advantage of treating cardboard mortars aside from durablility?
Does this increase performance or safety factors?
Just curious.