How to re-coat a shelter?

Since last year I’ve received several further questions about the re-coating of my tarp. I had made a rather brief post about it, without explaining my method in much detail. Now as I’ve re-coated my tarp again a few weeks ago, I now can show you a more comprehensive explanation about my method. This post will probably bring no news to many of you, but for those who don’t have experience with coating a shelter and like to hear my method, I hope it will further clarify the process.

Amblève 201203
The fabric of a new shelter (this is Willem’s silnylon Solo Trailstar on its very first pitch) should repel water droplets perfectly for many years.

Why and when re-coating a shelter?

During my recent trip to the Verdon, I noticed the fabric of my tarp was starting to suck up moisture on a few spots again and rain droplets didn’t bead up nicely anymore everywhere on the fabric. As soon as you notice the fabric of your shelter doesn’t repel water anymore it is wisely to re-coat your shelter, especially if you have plans to make a longer trip with it soon. If you don’t and let the coating further degrade, the fabric of your shelter will start to suck up moisture each time in the rain or on a condense loaded morning and will become more heavy then necessary. Furthermore the fabric will become very slow to dry once saturated. The ultralight silnylon fabric, which is used in lightweight tarps and shelters today, will even start to mist in heavier rain and you eventually risk to get wet under your shelter. Spinntex/spinnaker fabric (though not used anymore in new shelters these days it seems) will even start to leak quite badly. This misting or leaking does not happen with all tent fabrics however. I’ve never noticed any leaking through kerlon fabric of Hilleberg tents, even when the coating was totally eroded, though once the coating is degraded Hilleberg tents will suck up a lot of moisture also as all other tents will do. A new shelter doesn’t need a new coating soon and the water repellency should remain working for many years at best, though after those years of use you’ll notice the coating on the fabric will eventually degrade. The fabric will start to suck water and you should think about re-coating your shelter for the first time. As soon as you’ve applied a first coating yourself after the first degradation, you’ll have to re-coat the fabric again every one to four years depending on your frequency of usage as your own new applied coating will degrade too over time.

Amblève 201203
On my Grace Solo Spinntex tarp the coating recently showed signs of degradation, though not really noticeable in this picture.

Can I re-coat every shelter?

Shelters made out of cuben fabric never need re-coating. All other fabrics do have a coating which will degrade over their lifespan, mainly due to rubbing, the degrading effect of UV light from the sun and storing it wet. Shelter fabrics usually have either one of those two coatings: a silicone coating or a PU-coating (polyurethane). Tent floors usually have a PU-coating while tent flysheets usually have a silicone coating. However, a PU-coating is still used by some manufacturers on their tent flysheets. It is important to know which kind of coating has been applied to your shelter as each of these two kind of coatings need another product and solvent for re-coating. Some tents like for example those of MSR even have a different coating on each side of the fabric of the tent fly, a silicone coating on the outside and a PU-coating along the inside. If you’re not sure about the type of coating, try to contact the manufacturer.

Coatings based on silicone are the easiest to renew. In case of a PU-coating it is more difficult to find the right product and solvent. Most outdoor stores also sell a specific product that can be used to re-coat or revive the water repellency of your shelter, like for example Nikwax Tent and Gear SolarProof. You can use these, but I find them very expensive if you want to coat a whole tent compared to what you can do yourself with products from the hardware store and I’ve found Nikwax’s solution less effective and durable then my own re-coating method.

Ok, what do I need?

These are the necessary items for a silicone coating:

  • White spirit
  • A tube of silicone: transparent and odorless (without additives)
  • A silicone syringe
  • A clean pot or jar
  • An accurate weighing scale (one gram accuracy recommended)
  • A paint brush
  • A pair of protective gloves (you’ll notice I didn’t wear gloves but you should know better)

Re-coating the tarp
What is needed (notice I forgot a pair of protective gloves).

For a PU-coating you’ll need an urethane based product and an appropriate solvent. I’ve no experience yet with adding a PU-coating so I cannot give advice about what exact products to search for. Anyone with experience with applying a PU-coating, please feel free to share your experiences. You can also try the expensive option like Tent Sure Tent floor sealant from Mcnett or the Nikwax variant. Otherwise the method for a PU-coating will be rather similar as I’m going to explain for a silicone coating.

This is the method I use:

  • I pitch the tarp or tent in a way so that it is easy to reach the fabric. Best is to choose a well ventilated place. Just outside in the garden is the place I recommend. It is not a good idea to try re-coating inside the house as your house will smell for days and become dangerously unhealthy to live in! I’ve once re-coated a tent in the garage with the garage door wide open. Even in these circumstances I had to pause regularly to search for a fresh breath of air because I started to get dizzy from the dangerous odor of the white spirit. Outside in the garden I’ve never had that problem so I really recommend to do it outside. Choose a day with the correct weather forecast, this is not too windy and no rain if you don’t have a roof available. However during the spring season there might be a lot of anther dust and/or fluff hovering in the air during fair weather days. This will creep into the coating while drying so I try to avoid this type of days, even though it is not a disaster if some anther dust gets embedded in the coating. Sticking fluff is another matter however.

Recoating Hilleberg Akto
To coat the Hilleberg Akto I used two battens nailed together at the centre and pitched the tent onto it with the aid of nails beaten on the slats at the right places. This way you can put the tent upright against a wall and easily reach the fabric everywhere. I use this method also to simply wash my tents after a trip. You can follow a similar approach with many other tents.

  • Then I clean the tent or tarp from any dirt and oils that have accumulated on the fabric during its usage. I do this by washing the fabric with a non aggressive soap (like Nikwax Techwash or plain simple dish soap), rinse well with water afterwards and rub dry with a towel. Be sure the fabric is completely dry before you start with painting.

Re-coating the tarp
Cleaning the tarp from any dirt.

  • Then I prepare the silicone mixture. This is done by pouring white spirit and silicone into a clean pot or jar in a weight ratio of about 15:1 respectively. This means I have 15 times the weight of white spirit in the pot compared to silicone. How many silicone should you take? I count for about 1,5 grams of silicone per one square meter of fabric for one layer on one side. So for the Trailstar for example which has a fabric area of about 10,5m² or 21,0m² for both sides and if I would choose to apply one layer to the inside and two layers on the outside, I should then take a total of 47 grams (3 layers x 1,5 grams x 10,5m²) of silicone and 705 grams of white spirit. Then I stir well with the brush in the pot until all the silicone is dissolved into the white spirit. This might take a while. If the silicone is very difficult to dissolve you can try to warm up the mixture a bit (don’t exaggerate!). At warmer temperatures I’ve noticed that silicone dissolves easier into the solvent.

Re-coating the tarp
Preparing the mixture of silicone and white spirit by weighing accurately on a scale.

  • Then I paint the fabric with the silicone mixture as evenly as possible and keep attention to avoid running droplets on the fabric. After adding one layer, I let it dry and once dried I paint another layer on top of the first one if necessary. Normally one layer should be sufficient for silnylon. Spinntex however needs a thinker coating and thus two or three layers for a longer lasting water repellency. Or in case the initial coating on silnylon or tent fabrics has already been very degraded, two layers on the outside might be more advantageous over a single layer only. Once dried, I rub over the new coating with my fingers. This way I can judge if the coating is thick enough to my liking or if yet another (possibly thinner) layer might be desirable. To control the thickness of the new coating you can off course play with the mixing ratio between silicone and white spirit (choose between 20:1 and 10:1) and the amount of layers painted, judge for yourself.

Re-coating the tarp
Painting the first layer on the inside.


Re-coating the tarp
Applying a second layer on the outside after the first layer has dried out.

  • As soon as the whole tent/tarp is coated, I let everything dry sufficiently for several hours till the coating is clearly dried out and doesn’t stick anymore. Sunlight and a breeze speeds the drying process remarkably. Sprinkling talc powder or anything similar on the fabric afterwards is absolutely not necessary (as is sometimes done with seam sealing). Afterwards you will notice the tarp/tent will show a slightly difference in shade over the fabric because it will be impossible to paint an exactly even coating. While some might find this not appealing, I personally don’t worry about it as the shading difference will gradually fade away with use during the first few trips as the coating degrades again.

Recoating Hilleberg Akto
After re-coating the fabric will show irregular differences in shade/color. This will weaken while drying and further fade away during the first weeks of use.

Recoating Hilleberg Akto
As soon as the new coating is completely dry, you can run a test. The water repellency should be 100% again, droplets will bead on the fabric and repel instead of being absorbed by the fabric.

Now your tarp or tent has a new coating and will be ready for many more trips. Hope my explanation has been helpful to you.

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19 thoughts on “How to re-coat a shelter?

  1. Interesting, thanks for the Tutorial! The reason why Cuben does not have to be recoated is because it breaks before ;)
    best,
    Matthias

  2. Can’t you aplly the stuff with a “velvetroller” instead of a paint brush? Would there be less difference in color?

  3. Good Article. I generally feel that a 15-20:1 ratio for sealing older silnylon is fine. Note that it does NOT penetrate old coatings, only uncoated fabrics and open pores(broken coatingings) between threads. For this reason I highly recommend you do both sides at least one coat for a more permanent bond. Also, if the coating is too thick, it will peel. It is easier to add a second, thinner coat afterwards, than trying to remove a too thick coat. Any doubt on the mix should always err on the side of thinner.

    One thing that was not mentioned was fabric stretching. This can happen in higher winds, or on tarps, flys, etc near and around stress areas. This will also lead to a break down of the origonal coating in those areas. This happens at an accilerated pace, beyond what you mention. But, it is difficult to guage usage for individual users. Suffice it to say, that wet out of the fabric usually indicates a break down of the coating in these areas, even if the majority of the fabric is still good.

  4. Any specs on weight before and after re-coating? Is there much of a difference with multiple layers, thinner/thicker ratios, etc? Great article!

    • The weight gain is simply the amount of silicone in the new coating. I’ve only weighted the difference once and have noticed that not all silicone in the mixture will be effectively transferred to the new coating. There will always be a small amount remaining in the pot and on the brush. However with silnylon you don’t need to apply a thick coating so the weight gain will not be significant.

  5. Hoi Dzjow .

    Vind je het erg als ik in het Nederlands schrijf. Dat pent iets makkelijker.
    Zeer interessant artikel! Ik wil dit ook wel proberen. Ik heb mijn oude noodparachute al eens opgezet als een shelter. die shelter ziet er goed uit om een kleine groep te herbergen. De stof is echter verre van waterdicht. Het oppervlak is echter heel groot. Dus vraag ik me af hoe ik dit best aanpak. Opspannen zodat ik het gehele oppervlak kan bereiken is niet mogelijk.
    ik overweeg :
    A/ In stukken werken => Dit gaat lang duren …
    of hoog opspannen en de onderkant insmeren => Ik vermoed dat dit te veel zal druipen?
    of de doek op een plastiek zeil leggen, insmeren, eenmaal ingesmeerd opspannen om te drogen => ik vermoed dat , als de silicone is doordrongen tot op het onderliggend zeil en daarna opgehoffen , zal het oppervlak ook wel niet effen zijn.
    of spuiten met het verfpistool.
    met uw ervaring , hoe schat jij dit in?
    groeten peter.

    • Hoi Peter,

      Met een hele parachute heb ik geen ervaring dus is ook maar giswerk van mijn kant. Ondersteboven schilderen gaat de smurrie over de borstelsteel op je armen lekken. Ik denk dat je best op een plastiek werkt zoals je zegt en geen te groot oppervlak in één keer probeert te schilderen en alle eventuele oneffenheden nog snel egaal schildert als je het hebt opgehangen om te drogen. Of misschien kan je een groot deel van de parachute ook verticaal ophangen over een touw of wasdraad met een hele hoop wasspelden en onderaan fixeren tegen de grond met gewichten, eventueel in een lat gedraaid. Zo zou je toch in een paar keer vrij snel heel de parachute moeten kunnen coaten? Veel succes ermee alvast.

  6. Peter, I have a question, does your re-coating affect the breathability of the original material?

    • Deborah, I don’t know what you intend to do but the method I described here is only useful for non-breathable fabrics like tent flysheets and groundsheets. Breathable fabrics like in outdoor clothing (those labeled with gore-tex, eVent and the like) will be ruined if you treat them with a silicone coating. These fabrics should be washed with a non detergent soap and be treated with a DWR treatment to renew water repellency and thus the breathability of the fabric and not with the method described in this post. Hope this is clear.

    • Ik heb mijn parachutte een tijdje geleden ge recoat met een spuitpistool.
      (om te gebruiken als chelter/ niet meer als parachutte uiteraard) De chelter opgezet in de tuin en spuiten maar. De verdeling ging vrij goed. Maar om enkele liters aan te brengen op het gigantische doek ben je wel even bezig. Eerlijk gezegd zou ik het niet aanraden om In vernevelde vorm dergelijke hoeveelheden aan te brengen . Dit kan niet gezond zijn. Naar het einde van de job toe dacht ik kortademig “waar ben je mee bezig? Dit is het niet waard.” de stof is niet zo veel verzwaard. (wat de bedoeling was.) Het water parelt er nu af , maar je kunt er nog steeds licht door blazen. Dus ik verwacht niet dat je bij langdurige of hevige regen het er droog gaat onder houden. Met de borstel of onderdompeltechniek ga je dikkere laagdiktes aanbrengen die waterdichter zijn maar ook een pak zwaarder uiteraard.
      Als het er eens van komt de groepschelter uit te testen laat ik wel iets weten.
      groeten pe

  7. Great post. I would like to try this method on my Henry Shires Double Rainbow sil-nylon tent when I have time at home. I am on the trail and the tent’s waterproofing seems to be suffering. Do you have a “wash-in” or “spray on” product of preference if one is on the trail and needs a quick fix that is not as involved as your method? You mention Nikwax Solar & Gear proof, but I thought I heard that is not intended for sil nylon. Any other suggestions? I would definitely need to first clean with Tech Wash or dish soap as the tent is quite dirty. Any help would be greatly appreciated!

  8. Hi Dzjow, Any advise/experience when the old coating is already very much deteriorated (peeling)? Just painting over it or trying to dissolve it first through a solvant bath? (I am trying to rejuvenate a tent which has suffered from tough climate conditions…

    • Hi Pierre, I would always try to paint a new coating on the original one, but when the coating is really peeling off as you say, this is maybe not going to stop the problem. I have no experience with your problem and I’m not sure if trying to apply a new coating after you’ve dissolved the original one is going to give you a perfect result. Anyway, it may be worth trying.

  9. Hi Dzjow,
    thank you very much for your helpful and informative article. If I’m not wrong you only described a method to re-coat silicone based coating. Do you also have experience with am “home-made” method to re-coat PU-based coatings?
    Kind regards from Laos

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